* Add FLATBUFFERS_COMPATIBILITY string
- Add a new __reset method NET/JAVA which hides internal state
* Resolve PR notes
* Use operator new() to __init of Struct and Table
* Restrict visibility of C# Table/Struct to internal level
Include C# codegen in flatc and .NET FlatBuffer access via the
FlatBufferBuilder class
Tested: on Windows.
Change-Id: If5228a8df60a10e0751b245c6c64530264ea2d8a