Platformer 2d sample

Finally finished testing and polishing the Platformer 2D sample for the MonoGame 3.2 release.

Covers all currently supported (public) platforms, including:

* Android (using MG 3.2 NuGet)
* iOS (using MG 3.2 NuGet)
* MacOS (using MG 3.2 NuGet)
* Ouya (Using direct ref to source - update when testing)
* PSM (Using direct ref to source - update when testing)
* WindowsGL (using MG 3.2 NuGet)
* Windows 8 (using MG 3.2 NuGet)
* Windows Phone (using MG 3.2 NuGet)

All tested and working properly.