C# binding

[bramhoven]

This is still a W.I.P. but I wanted to publish it already in case anybody had any feedback or improvements!

This would be the PR for #152

[VivekPanyam]

Nice work!

I didn't look at the changes in depth yet, but here's a high level note so far:

Can you create a .gitignore file inside source/carton-bindings-csharp/ and ignore all the autogenerated files?

Also, can you add a build script in that directory that generates files and builds the library?

That should make this PR much smaller than the 16k lines it currently is :)

Thanks for spending time on this!

[bramhoven]

@VivekPanyam I added the .gitignore, so it should be more readable now!

[VivekPanyam]

Can you also add cross-platform-ast.json and the *.gen.cs files to source/carton-bindings-csharp/.gitignore as well please?

Also, feel free to mark the PR as ready for review when it's ready for a more in-depth review!