Fixed rare error that could occur when no walls are in the vicinity of a pawn.

Implemented a new feature: Mental breaks can cause a grafitti painting spree.

• Graffiti is no longer considered filth but art (ugly art)
  
• Cleaning graffiti is now its own Job with lower priority than cleaning filth.
  
• Pawns should first clean vomit and blood on the floor before cleaning graffiti.

• Added an additional graffiti texture for more variety and altered some obnoxious ones.
  
• Fixed loading bug introduced with last patch

* Fixed bug that prevented cleaning

* "Fixed" spelling mistake in the preview image (graffiti <-> graffity)

* Fixed graffiti on walls with double thickness
* Fixed graffiti magically cleaning itself after loading a save game

[Auto-generated text]: Initial upload.