Fixed BlendState.ToString() to not display "Opaque" for all custom states.
Fixed BlendState.ToString() to display the short type name instead of the full namespace-qualified type name.
Added ToString() to DepthStencilState and RasterizerState which will identify if the state is one of the preallocated static states.
Merge branch 'BlendStateToString' into stable_BtA

Conflicts:
	MonoGame.Framework/Graphics/States/BlendState.cs