Add IconButton

Silica has two types of buttons - buttons with text (Button) and buttons with images (IconButton).
This kinda makes sense and switching this at runtime would be difficult and modRana does not
really mix images and text on buttons anyway. For controls, regular Button is used if IconButton
is requested.
Icon Button needs checkable & checked
No need to push the map page if it is already set as initialPage
Use icon buttons for icon only buttons