boost_test_jamfile with better parsing

I started working on an improved Jamfile parser for `boost_test_jamfile`.

The new version should recognize the following tests
```
test-suite foo
[ run some_test.cpp ]
;

run
some_test.cpp
;

run some_test : my_arg ;
```

I think it would be much easier to write the parser in Python and call it from CMake than implementing the logic with CMake capabilities. Would that be a show-stopper? And is it really useful to have an imperfect Jamfile parser in CMake? An alternative is to provide a Python script which generates the whole CMakeLists.txt from an existing Jamfile.
```
+ Still easy to convert simple Jamfile files to cmake
+ You can edit special cases not handled by the parser
- Needs to be run manually
```