Start re-organizing demos so the physics setup can be shared easier (explicit create graphics objects, init/exit physics etc)

Add B3G_RETURN key code, only implemented in Windows so far (todo: Mac, Linux)
Fix Windows key management (use WM_CHAR event instead of WM_KEYUP
Add Return (OnKeyReturn) key support TreeNode, so we can select an item using the return key.

Demos/BasicDemo/BasicDemo.cpp

@@ -123,8 +123,8 @@ void	BasicDemo::initPhysics()
 	setShadows(true);
 
 	setCameraDistance(btScalar(SCALING*50.));
-
-	m_physicsSetup.initPhysics();
+	GraphicsPhysicsBridge gfxBridge;
+	m_physicsSetup.initPhysics(gfxBridge);
 
 	m_dynamicsWorld = m_physicsSetup.m_dynamicsWorld;
 	m_dynamicsWorld->setDebugDrawer(&gDebugDraw);