Prompt the user to use the latest CMake

### Brief Issue Summary
I have successfully got my project to configure (and build):

```
[main] Configuring folder: odin-data
[main] For the best experience, CMake server or file-api support is required. Please upgrade CMake to 3.7.1 or newer.
[proc] Executing command: /usr/bin/cmake --no-warn-unused-cli -DHDF5_ROOT:STRING=/dls_sw/prod/tools/RHEL7-x86_64/hdf5/1-10-5/prefix -DLOG4CXX_ROOT_DIR:STRING=/dls_sw/prod/tools/RHEL7-x86_64/log4cxx/0-10-0dls2/prefix -DBLOSC_ROOT_DIR:STRING=/dls_sw/prod/tools/RHEL7-x86_64/c-blosc/1-14-2/prefix -DCMAKE_EXPORT_COMPILE_COMMANDS:BOOL=TRUE -DCMAKE_BUILD_TYPE:STRING=Debug -DCMAKE_INSTALL_PREFIX:STRING=vscode_prefix -DCMAKE_C_COMPILER:FILEPATH=/usr/bin/gcc -DCMAKE_CXX_COMPILER:FILEPATH=/usr/bin/g++ -H/scratch/work/tools/RHEL7-x86_64/odin-data -B/scratch/work/tools/RHEL7-x86_64/odin-data/vscode_build "-GUnix Makefiles"
[cmake] Not searching for unused variables given on the command line.
[cmake] -- Boost version: 1.53.0
[cmake] -- Found the following Boost libraries:
[cmake] -- program_options
[cmake] -- system
[cmake] -- filesystem
[cmake] -- unit_test_framework
[cmake] -- date_time
[cmake] -- thread
[cmake] -- regex
[cmake] -- Root dir: /dls_sw/prod/tools/RHEL7-x86_64/log4cxx/0-10-0dls2/prefix
[cmake]
[cmake] Looking for log4cxx headers and libraries
[cmake] -- Include directories: /dls_sw/prod/tools/RHEL7-x86_64/log4cxx/0-10-0dls2/prefix/include/log4cxx
[cmake] -- Libraries: /dls_sw/prod/tools/RHEL7-x86_64/log4cxx/0-10-0dls2/prefix/lib/liblog4cxx.so
[cmake]
[cmake] Looking for ZeroMQ headers and libraries
[cmake] -- Include directories: /usr/include
[cmake] -- Libraries: /lib64/libzmq.so
[cmake]
[cmake] Looking for pcap headers and libraries
[cmake]
[cmake] Looking for blosc headers and libraries
[cmake]
[cmake] Looking for kafka headers and libraries
[cmake]
[cmake] Searching for HDF5
[cmake] Determining odin-data version
[cmake] -- Searching Blosc Root dir: /dls_sw/prod/tools/RHEL7-x86_64/c-blosc/1-14-2/prefix
[cmake] -- Found Blosc: /dls_sw/prod/tools/RHEL7-x86_64/c-blosc/1-14-2/prefix/lib/libblosc.so
[cmake] -- Found Kafka: /usr/lib64/librdkafka.so
[cmake] -- HDF5_ROOT set: /dls_sw/prod/tools/RHEL7-x86_64/hdf5/1-10-5/prefix
[cmake] -- Git describe version: 1.4.0-59-g18d7a0c-dirty
[cmake] -- major:1 minor:4 patch:0 sha1:g18d7a0c-dirty
[cmake] -- short version: 1.4.0
[cmake] -- HDF5 include files: /dls_sw/prod/tools/RHEL7-x86_64/hdf5/1-10-5/prefix/include
[cmake] -- HDF5 libs: /dls_sw/prod/tools/RHEL7-x86_64/hdf5/1-10-5/prefix/lib/libhdf5.so/dls_sw/prod/tools/RHEL7-x86_64/hdf5/1-10-5/prefix/lib/libhdf5_hl.so
[cmake] -- HDF5 defs:
[cmake] -- HDF5 include files: /dls_sw/prod/tools/RHEL7-x86_64/hdf5/1-10-5/prefix/include
[cmake] -- HDF5 libs: /dls_sw/prod/tools/RHEL7-x86_64/hdf5/1-10-5/prefix/lib/libhdf5.so/dls_sw/prod/tools/RHEL7-x86_64/hdf5/1-10-5/prefix/lib/libhdf5_hl.so
[cmake] -- HDF5 defs:
[cmake] -- Configuring done
[cmake] -- Generating done
[cmake] -- Build files have been written to: /scratch/work/tools/RHEL7-x86_64/odin-data/vscode_build
```

I would like to use a different version of cmake than is installed in /usr/bin/cmake. When I set `cmake.cmakePath`, making my full `settings.json` the following:

```
{
"cmake.cmakePath": "/dls_sw/prod/tools/RHEL7-x86_64/cmake/3-9-6/prefix/bin/cmake",
"cmake.generator": "Unix Makefiles",
"cmake.buildDirectory": "/scratch/work/tools/RHEL7-x86_64/odin-data/vscode_build",
"cmake.installPrefix": "vscode_prefix",
"cmake.sourceDirectory": "/scratch/work/tools/RHEL7-x86_64/odin-data",
"cmake.configureSettings": {
"HDF5_ROOT": "/dls_sw/prod/tools/RHEL7-x86_64/hdf5/1-10-5/prefix",
"LOG4CXX_ROOT_DIR": "/dls_sw/prod/tools/RHEL7-x86_64/log4cxx/0-10-0dls2/prefix",
"BLOSC_ROOT_DIR": "/dls_sw/prod/tools/RHEL7-x86_64/c-blosc/1-14-2/prefix"
}
}
```

I get this output:

```
[variant] Loaded new set of variants
[kit] Successfully loaded 2 kits from /home/mef65357/.local/share/CMakeTools/cmake-tools-kits.json
[main] Configuring folder: odin-data
[rollbar] Unhandled exception: Unhandled Promise rejection: Post-folder-open Error: connect ENOENT /tmp/cmake-server-0.247112383440653 {"folder":{"uri":{"$mid":1,"fsPath":"/scratch/work/tools/RHEL7-x86_64/odin-data","external":"file:///scratch/work/tools/RHEL7-x86_64/odin-data","path":"/scratch/work/tools/RHEL7-x86_64/odin-data","scheme":"file"},"name":"odin-data","index":0}}
```

(If I comment out the `cmake.cmakePath`, it works, as in the first snippet.)

### Expected:
I would expect this to work as it does if I run the full command on the command line:

```
$ cd /scratch/work/tools/RHEL7-x86_64/odin-data/vscode_build
$ /dls_sw/prod/tools/RHEL7-x86_64/cmake/3-9-6/prefix/bin/cmake -DHDF5_ROOT=/dls_sw/prod/tools/RHEL7-x86_64/hdf5/1-10-5/prefix -DLOG4CXX_ROOT_DIR=/dls_sw/prod/tools/RHEL7-x86_64/log4cxx/0-10-0dls2/prefix -DBLOSC_ROOT_DIR=/dls_sw/prod/tools/RHEL7-x86_64/c-blosc/1-14-2/prefix -DCMAKE_INSTALL_PREFIX=../vscode_prefix ..
-- Boost version: 1.53.0
-- Found the following Boost libraries:
-- program_options
-- system
-- filesystem
-- unit_test_framework
-- date_time
-- thread
-- regex
-- chrono
-- atomic

Looking for log4cxx headers and libraries
-- Root dir: /dls_sw/prod/tools/RHEL7-x86_64/log4cxx/0-10-0dls2/prefix
using pkgconfig
-- Checking for module 'log4cxx'
-- No package 'log4cxx' found
-- Include directories: /dls_sw/prod/tools/RHEL7-x86_64/log4cxx/0-10-0dls2/prefix/include/log4cxx
-- Libraries: /dls_sw/prod/tools/RHEL7-x86_64/log4cxx/0-10-0dls2/prefix/lib/liblog4cxx.so

Looking for ZeroMQ headers and libraries
-- Include directories: /usr/include
-- Libraries: /lib64/libzmq.so

Looking for pcap headers and libraries

Looking for blosc headers and libraries
-- Searching Blosc Root dir: /dls_sw/prod/tools/RHEL7-x86_64/c-blosc/1-14-2/prefix
-- Found Blosc: /dls_sw/prod/tools/RHEL7-x86_64/c-blosc/1-14-2/prefix/lib/libblosc.so

Looking for kafka headers and libraries
-- Found Kafka: /usr/lib64/librdkafka.so

Searching for HDF5
-- HDF5_ROOT set: /dls_sw/prod/tools/RHEL7-x86_64/hdf5/1-10-5/prefix
Determining odin-data version
-- Git describe version: 1.4.0-59-g18d7a0c-dirty
-- major:1 minor:4 patch:0 sha1:g18d7a0c-dirty
-- short version: 1.4.0
-- HDF5 include files: /dls_sw/prod/tools/RHEL7-x86_64/hdf5/1-10-5/prefix/include
-- HDF5 libs: /dls_sw/prod/tools/RHEL7-x86_64/hdf5/1-10-5/prefix/lib/libhdf5.so/dls_sw/prod/tools/RHEL7-x86_64/hdf5/1-10-5/prefix/lib/libhdf5_hl.so
-- HDF5 defs:
-- HDF5 include files: /dls_sw/prod/tools/RHEL7-x86_64/hdf5/1-10-5/prefix/include
-- HDF5 libs: /dls_sw/prod/tools/RHEL7-x86_64/hdf5/1-10-5/prefix/lib/libhdf5.so/dls_sw/prod/tools/RHEL7-x86_64/hdf5/1-10-5/prefix/lib/libhdf5_hl.so
-- HDF5 defs:
-- Found Doxygen: /dls_sw/prod/tools/RHEL7-x86_64/defaults/bin/doxygen (found version "1.8.13") found components: doxygen dot
-- Configuring done
-- Generating done
-- Build files have been written to: /scratch/work/tools/RHEL7-x86_64/odin-data/vscode_build
```

### Platform and Versions

- **Operating System**: RedHat Enterprise Linux 7.7
- **CMake Version**: 2.8.12.2 / 3.9.6
- **VSCode Version**: 1.43.1
- **CMake Tools Extension Version**: 1.3.1
- **Compiler/Toolchain**: GCC 4.8.5

### Other Notes/Information

Thanks!

Start with the CMake Tools handling of the `cmake.cmakePath` setting and the post-folder-open flow that reports `ENOENT /tmp/cmake-server-...`. Reproduce with CMake Tools 1.3.1, VS Code 1.43.1, and CMake 2.8.12.2 versus 3.9.6, then compare the extension command with the working command-line invocation. Done means selecting the configured newer CMake works without the CMake server connection error.

Written by the indexing model from the issue text.