Dirty Stations

During game setup, all floors on the station will have a chance of spawning a cleanable decal.  The decals are area-sensitive and the probability is tiered:
0% chance - The chapel and library are never dirty, as well as Centcomm, some tile types, etc.
33% chance (1/3) - Ultra-dirty areas such as the mining station and the derelict.
6.7% chance (1/15) - High-dirt areas such as maintenance and engineering.
1.7% chance (1/60) - Average/low dirt, includes most of the station.

The cleanables are blood, gibs, vomit, dirt, oil, flour, egg splats, robot debris, and the occasional self-cleaning radioactive spill (which is hardly worth putting in).

Additionally, this adds "old" versions of suspicious cleanables (blood, gibs, vomit, and robot parts).  This could be re-sprited, but in the meantime, an icon operation darkens and discolors them.  The names and descriptions of these are also modified to make clear that they are not recent.

Old blood, gibs, and vomit:
https://dl.dropbox.com/u/1190647/SS13/old_crud.png