Added changes for demo
project changes
Merge branch 'physics' of github.com:codeLogik/XNA_GameEngine_CS680 into physics

Conflicts:
	XNA_GameEngine/XNA_GameEngine/XNA_GameEngine/CoreMain.cs
	XNA_GameEngine/XNA_GameEngine/XNA_GameEngine/XNA_GameEngine.csproj.Debug.cachefile
	XNA_GameEngine/XNA_GameEngine/XNA_GameEngineContent/XNA_GameEngineContent.contentproj