[tkmodel] Start to work on tkmodel using AssimpNet
[Toolkit.Compiler] Update to latest Assimp.NET. Recompile assimp binaries to use latest FBX support
[Toolkit.Graphics] Add Material for ModelData
[Toolkit.Compiler] Simplify MaterialKey
[Toolkit.Compiler] Finish support for Model compiler, tkmodel command line and msbuild task
[Toolkit.Compiler] Finish support for Model compiler, tkmodel command line and msbuild task
[Toolkit.Graphics] Add Model classes. First implem draft, not yet tested.