[TIMOB-8792] MobileWeb: Clean up UI Inheritence and create "core" controls

We should create two "core" or "simple" controls for text and images. ImageView and Label are really heavy weight and are reused elsewhere...creating a simplified version that is used by those two controls, and any controls that use them, should give us a performance improvement (especially in memory usage). These controls should inherit from Element to keep them lightweight. We should go ahead and do the inheritence switch as Element->Widget->View, and move things like _add(), borders, etc into Widget to try and lighten up Element.