more accurate check than previously; because the normal isOnScreen()
uses a bounding circle check... which gets pretty large for something
that spans the entire screen width.
class Element is completely gone.
(The files are still there but no longer compiled in. Will delete later)
Broken still:
- support for vertical flip
- the editor
- culling
This takes out the last of the RenderObject mutables.
This also fixes the long-standing editor bug that map tiles
that are once moved to parallax layers and then back to a
normal layer keep their scroll factor until the tile is deleted
or the map saved and reloaded.
