feature: Implement height editing in map editor

[IceReaper]

Concider this a draft!

Basic implementation of height editing in the map editor.

Open topics:

• Re-calculation of tiles and ramps is currently missing.
• Due to above restriction, the Extend option does currently not extend the changed tiles outside of the brush.
• It seems the mousewheel cannot be processed in the brush for easier brush size manipulation.
• We might want to be able to change the editor keys via the settings?