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.

btgui/GwenOpenGLTest/OpenGLSample.cpp

@@ -308,7 +308,7 @@ int main()
 	b3gWindowConstructionInfo wci;
 	wci.m_width = sWidth;
 	wci.m_height = sHeight;
-	wci.m_resizeCallback = MyResizeCallback;
+//	wci.m_resizeCallback = MyResizeCallback;
     window->createWindow(wci);
     
 	window->setResizeCallback(MyResizeCallback);