Visual Studio support

[FiniteReality]

We'll need to write a CPS... something or other for this. I'm not the most familiar with Visual Studio internals, so my efforts until now have mostly been focused on the .NET and MSBuild command line.

[FiniteReality]

I figure I should probably give an update here since this project has looked somewhat dead recently (I've been full-time employed for the past few months, and had a lack of motivation for the past few months before that):

• I have an extension in progress that advertises cxxproj support
• I'm working my way through figuring out the Visual Studio SDK and making sure I get the right project stuff loaded
  • There's lots of conflicting resources here, and the .NET Core project system isn't super easy to understand either
  • Figuring out where I've gone wrong is really hard since Visual Studio doesn't give any details (as far as I can tell...)
• There's a bug with clang detection (oops.) which makes it seem like Windows isn't supported
• I need to additionally detect visual studio installs to search for clang to allow dotnet build/dotnet msbuild