Reactivates Away Gate (#528)

* Added stomach.ogg and stomach tiles for later

* Updated some gateway maps, added new (unfinished) one

* Snowfield progress

* This map is pretty much done!

* Return of the Gateway Maps

* Optimization of various shit.

* Copies a small fix from Polaris

https://github.com/PolarisSS13/Polaris/pull/2414

* Changed vore mob knockdown chance. Map fixes.

* Datraen corrects outstanding issues with away missions, separates certain parts of code into their own procs. (#532)

* Final commit.

- Tried to fix vore mobs not attacking prey once they are disabled.
- Various map fixes to be consistent with fixed gateway setup.
- Gave Markov bad grammar.
- Fixed polar bears not dying.
- Modernized all gateway maps except the clown temple which is still
broken.

code/controllers/master_controller.dm

@@ -33,9 +33,6 @@ datum/controller/game_controller/New()
 datum/controller/game_controller/proc/setup()
 	world.tick_lag = config.Ticklag
 
-	spawn(20)
-		createRandomZlevel()
-
 	setup_objects()
 	setupgenetics()
 	SetupXenoarch()