Preliminary implementation of ZAS as a StonedMC subsystem.

* Creates the SSair subsystem which replaces the Setup, Start(), and Tick() procs of air_master.
* It may be best to have SSair completely replace air_master, but for now we are having them work together.   It does completely replace the old processScheduer air ticker however.
* Remove the obsolete Setup and Tick procs.
* Adjust admin and debug verbs that dealt with some ZAS internals to work with the new implementation.

code/modules/admin/admin_verbs.dm

@@ -779,11 +779,11 @@ var/list/admin_verbs_event_manager = list(
 	set category = "Debug"
 	set name = "Kill Air"
 	set desc = "Toggle Air Processing"
-	if(air_processing_killed)
-		air_processing_killed = 0
+	if(!SSair.can_fire)
+		SSair.can_fire = TRUE
 		usr << "<b>Enabled air processing.</b>"
 	else
-		air_processing_killed = 1
+		SSair.can_fire = FALSE
 		usr << "<b>Disabled air processing.</b>"
 	feedback_add_details("admin_verb","KA") //If you are copy-pasting this, ensure the 2nd parameter is unique to the new proc!
 	log_admin("[key_name(usr)] used 'kill air'.")

code/modules/admin/verbs/grief_fixers.dm

@@ -45,10 +45,7 @@
 
 	usr << "\[4/5\] - All turfs reset to roundstart values."
 
-	qdel(air_master)
-	air_master = new
-	air_master.Setup()
-	spawn air_master.Start()
+	SSair.RebootZAS()
 
 	usr << "\[5/5\] - ZAS Rebooted"
 	world << "<span class = 'danger'>Atmosphere restart completed in <b>[(world.timeofday - current_time)/10]</b> seconds.</span>"

code/modules/admin/verbs/mapping.dm

@@ -274,14 +274,7 @@ var/list/debug_verbs = list (
 	set name = "Reboot ZAS"
 
 	if(alert("This will destroy and remake all zone geometry on the whole map.","Reboot ZAS","Reboot ZAS","Nevermind") == "Reboot ZAS")
-		var/datum/controller/air_system/old_air = air_master
-		for(var/zone/zone in old_air.zones)
-			zone.c_invalidate()
-		qdel(old_air)
-		air_master = new
-		air_master.Setup()
-		spawn air_master.Start()
-
+		SSair.RebootZAS()
 
 /client/proc/count_objects_on_z_level()
 	set category = "Mapping"