Fixes bug where the WindowsPhone template will not work in Visual Studio 2013.
Extracted API-specific methods from GraphicsDevice
Copy GraphicsDevice.cs to API-specific files
GraphicsDevice API split
Whoops! Sloppy rename.
Collapse one-line if-endif-if to if-else
Fix accidental extra present on Win8
Retry double-present fix.
Merge pull request #2243 from SickheadGames/GraphicsDeviceSplit

Split GraphicsDevice on a per-API basis
TextureCubeReader ignore existingInstance

TextureCubeReader ignore existingInstance. As a result of this on WP8
when the app is deactivated/activated the ReloadAsset fails to reload
the Cube.

I applied the same fix to Texture3DReader although I didn't test it. The
fix is quite simple and should work.

I tried to make the code resemble as much the style of the
Texture3DReader.Read(...)
Cleanup VertexBuffer ifdefs
Copying out platform versions of VertexBuffer.
Deduplicating platform code in VertexBuffer
Extracted platform methods from IndexBuffer.
Platform copy for IndexBuffer.
IndexBuffer platform code split.
Fix for PSM
Fix index buffer usings for GLES
Fix ifdef for GLES
Fixing Ouya build.