Fixes and improvements to airlock painters.

-Airlock painters can now be used on finished airlocks to change their paintjob. Keep away from the Clown.
-Airlock painter description up to standards. It still shows the current ink level.
-Fixed a bug with painting airlock assemblies where painted glass airlocks deconstructed to assemblies reconstructed to airlocks would lose their glass status.
-Airlock painters now make a sound (effects/spray2.ogg) when used to paint an airlock.