D-35: Refactor of how the UI syncer renders views and performs frame view lifecycle callbacks

//TODO should change below to *VISIBLE STACK UPDATED
//TODO on change, should get stack of visible frames that should be rendered on screen at the mo, and pass them in turn to the UI type handlers (who can choose if they need to be rerendered or not)
//at moment have problem as if any of the stack is updated, this method is called, and a view can get multiple visibility callbacks without a change in visibility status
//plus! if the top frame is partially transparent, and the frame underneath is removed, this will not cause that underlying render change at present.

See #19 & #5

doridori / Pilot

D-35: Refactor of how the UI syncer renders views and performs frame view lifecycle callbacks #35