Multiples fixes for GamePrototype

- Added DrawContext.DrawRectangle
- Added Rectangle.Round extension method
- Added Sprite.ShouldDrawPixelPrecision
- Fixed SpriteAnimation frame now using Transform if available
- Fixed sprite visibility optimization to use Origin
- Added music test in SandboxScreen
Updated GameFramework.nuspec

- Added DefaultScreen.cs.pp as template when installing package
- Added SpriteFont.xnb in Content folder when installing package
Updated Windows.nuspec

- Added Program.cs.pp as template when installing package