Undo/redo now works, after a painful refactor. Still crashes some though
Preview now clears correctly
Undo/redo now works well for tile painting. Resource addition and
deletion is another matter
Merge branch 'UndoFixes' of https://github.com/Preece/TGL into UndoFixes
Cleaning up and moving things around
Removing old copies of moved files
Removed the old tile item class
TileCoord horsin
TileCoord is now a QPoint