Feature/csharp

[LukasHabring]

Added csharp as target language.
Unfortunately I had to remove gogoproto in order to do that.
Results should be binary compatible though.

[CLAassistant]

All committers have signed the CLA.

[jpmeijers]

I believe you are experiencing the same issue as java, documented in #30. Can you try that workaround?

After speaking to the gogoproto maintainer it sounds like an issue of proto3 dropping features that proto2 had, that gogoproto depends on. And that the java and dotnet proto compilers don't support proto2 properly.

https://stackoverflow.com/questions/41833044/c-sharp-code-generation-with-google-protobuf-proto2-files

protocolbuffers/protobuf#6067

[LukasHabring]

@jpmeijers Thank you for your reply. It should be fixed now.

[htdvisser]

I'm going to close this stale pull request. We don't intend to make any changes to this repository since V2 is permanently shutting down in December.