Fixed Game.Exit() crash on WinGL and Linux platforms.

We must not call Game.Tick() after Game.Exit().
Fixes issue #2605.
First implementation of ReflectiveWriter.
Added EnumWriter support.
Merge pull request #2614 from thefiddler/runloopfix

Fixed Game.Exit() crash on WinGL and Linux platforms.
Fixed tabs.
Merge pull request #2616 from SickheadGames/reflective_writer

ReflectiveWriter
Get platforms that return false in BeforeRun working again (Just Android...) refs #2615
Merge pull request #2617 from danzel/fix-android

Get android working again
First rough skeleton of IntermediateSerializer classes.
Added some of the implementation from the XmlImporter work.
Removed unused usings.
Merge pull request #2621 from SickheadGames/intermediate

IntermediateSerializer Skeleton
Fixed Texture2D.GetData on DirectX platforms
Added support for the element count parameter
This should fix GetData for Texture3D.Directx
Merge pull request #2622 from Nezz/getdatafix

Fixed Texture2D.GetData on DirectX platforms
Merge pull request #2623 from Nezz/getdata3dfix

Fix GetData for Texture3D.Directx
Added helpers to retrive all the ContentTypeSerializerAttribute types.
Fixed incorrect overload.
Added int, float, and string serializers.
Added more implementation references.
First pass at the ReflectiveSerializer.