Protogame now building successfully running on Android

Changes include:
  - Dx removed
  - Ninject, Newtonsoft.Json and protobuf-net added as submodules
  - AStarPathFinder removed as Protogame did not rely on it
  - Network asset manager disabled due to reliance on Dx; will be changed over in future
  - protobuf-net serializers are pregenerated, as portable protobuf-net does not support on-the-fly serialization / deserialization
  - DefaultProfilingInterceptor is unavailable on mobile platforms (but works under desktop platforms)
  - FileSelect UI element updated to only trigger under desktop platforms
  - DefaultKeyboardStringReader updated to not check caps lock status on mobile platforms
  - GameWindow property has been abstracted into an IGameWindow interface
Merge branch 'master' into mobile