Fix up focus issues with the new Application. Added tabChildren=true for group. Had to override Group's focusPane getter/setter b/c the UIComponent version uses addChild/removeChild which throws an RTE for Group. This should be revisited when focusPane is revisited (and maybe moved into the Skin...?)
Based on some comments from Glenn, removed backgroundColorNumber and just use backgroundColor typed as an Object.
QE: Yes - Will need to start writing tests for Application and focusing inside Groups