Holy shit air alarms work properly now. Yes, this time it's tested.
* Area air alerts are the maximum of all air alarm local danger levels.
* Doors are no longer fumbled and close upon alert level 2, and when all alert levels clear, the DOORS OPEN AUTOMATICALLY OH MY GOD
* Air alarm icons refresh properly and only show red in actually dangerous areas.  (Area alerts only cause yellow icons)
* Alerts clear automatically
* Silicons can set thresholds now (someone forgot an !)

Conflicts:
	code/game/area/areas.dm
	html/changelog.html