C# kcp for Unity.
- Kcp.cs based on kcp.c v1.7, line-by-line translation to C#
- Fixed WND_RCV bug from original kcp
- Optional high level C# code for client/server connection handling
- Optional high level Unreliable channel added
- Optional where-allocation KcpClient/Server/Connection NonAlloc versions
Pull requests for bug fixes & tests welcome.