Zombie Fortress 0.5.3 Released

This update is much smaller than I wanted and expected it to be. A few features that were going to be implemented seem to quite tricky.

Changes from 0.5.2 to 0.5.3:
- Zombie Regeneration! Heavies will now recover 10 hp/sec and scout's 4/sec.
- Scout ability redesign. Whenever a Sniper kills a zombie, they regain 25 health, 5 sniper rounds and 25 SMG rounds.
- New GUI help system that should help out new players who are too lazy to type out "zf_class" or "zf_help".
- Demomen now start with double primary ammo, sharing the ability with soldiers.
- You can only be a survivor 3 times in a row before being forced to be a zombie.
- Spies have lost the sapper but gained the disguise kit.
- The Axetingusher and Engineer Shotgun should no longer appear in play.

Current Code Length for 0.5.3: 953 (+133 from 0.5.2)