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/Gwen/Controls/TreeControl.cpp

@@ -72,8 +72,10 @@ void TreeControl::OnNodeAdded( TreeNode* pNode )
 	pNode->onNamePress.Add( this, &TreeControl::OnNodeSelection );
 }
 
+
 void TreeControl::OnNodeSelection( Controls::Base* /*control*/ )
 {
+	//printf("TreeControl::OnNodeSelection\n");
 	if ( !m_bAllowMultipleSelection || !Gwen::Input::IsKeyDown( Key::Control ) )
 		DeselectAll();
 }