Several small editor improvements.

- Removed a few dead members in the editor mode
- Removed the dead brush mode as it was replaced by tile dragging
already.
- Added tile coordinates, and tile type information next to the cursor
This way, you know what you are handling or dragging.
- Added a check to prevent adding walls on top of a creature.
- Added a check to prevent dropping a creature on a wall tile.
In that case, the creature will go back to its former position.