Added One_Screen_Example_Theme as a minimal example.
Report error on fetching empty string metric instead of crashing.
add first draft of ActorScroller example
draft 2 of ActorScroller example; still needs work
* removed QuantizePixels because it's unused
* make note that the "BitmapText requires ActorFrame for coloring" bug has existed for a while
* mention what offset actually is in TransformFunction