New SOS Extension Commands

Hi,

I have added a few fairly generic SOS extension commands to a fork of the .NET Core Diagnostics repository located at:

https://github.com/meriffa/diagnostics

**I am wandering if anyone has the cycles to review these and see if there is any value in merging them here.**

The new commands are:

* Data Export: comma-delimited, tab-delimited and JSON formatting
* DumpHeapExport: similar to dumpheap
* DumpModulesExport: list managed modules
* DumpStringsExport: list strings
* Enums & Structures:
* DumpEnumValues: list enum values
* DumpSingle: display float value
* DumpDouble: display double value
* DumpDecimal: display decimal value
* DumpDateTime: display DateTime value
* DumpTimeSpan: display TimeSpan value
* DumpDateOnly: display DateOnly value
* DumpTimeOnly: display TimeOnly value

All commands are included in the Microsoft.Diagnostics.ExtensionCommands project.

Thanks,

Marian.