CSS Pseudo Class support and element id support

Now supports pseudo classes (selected, highlighted, disabled) mainly for UIButton at the moment. Also lots of new properties - content insets for buttons, background image including resizable image support, and image on button. Visibility supported in the case where the CSS may control which elements are visible. Changed some "extended" properties to use -mobile- instead of -ios- on the hunch that we might want to make this work on Android someday. Also added id selectors based on values passed into registerView. Another push that builds on this is ready when this one is done and adds localized string support and lots of positioning features.