- fix glass stones: actors stuck beneath hollow stones
- fix swamp heat transformation - missing renaming
- reengineering st-plain:
- st-plain -> st_flat
- st-plain_hole -> st_flat_hollow
- st-plain_move -> st_flat_movable
- st-plain_break -> st_flat_breakable
- st-plain_cracked -> st_flat_cracked
- st-firebreak -> st_flat_burnable
- st-firebreak ->st_flat_moveburnable
- unify in a single class
- preserve identity on transformations
- hollow flat stone gets invisible on glasses