update child layout specs to test for reapply
OMG!  Removed motion_kit_id - element_ids are now specific to the layout.  This design makes things like 'get' much easier, but 'get(in:)' has been removed

get(:id) no longer builds the layout, but that could change
remove(:view) no longer removes subviews of get(:view) from the layout
gave a bunch of specs better names
removed the _root/@root stuff - no longer needed with simplified 'get' and element_ids