Serialization frontend over MessagePack-CSharp

Video talk about this repo (russian): https://www.youtube.com/watch?v=A1rliGwIRlc

1. Clone repo and a submodule. Be sure that symlinks are enabled.
2. Open ExampleProject at Unity.
3. Run 'DarkContractExample/NodeTest' and 'DarkContractExample/EntityTest' via menu.
4. Open 'DarkContractExample/DataExplorer' in separate window. Try to modify data, playtest scene. Note how data is restored.