Supply controller now holds a ref to it's shuttle

Instead of having to look it up every time.

Conflicts:
	code/game/supplyshuttle.dm
shuttle_controller now uses a shuttle datum

Conflicts:
	code/game/machinery/computer/communications.dm
	code/modules/admin/verbs/randomverbs.dm
	code/modules/mob/living/silicon/ai/ai.dm
	code/modules/power/singularity/singularity.dm
Adds escape pods to the controller
Forgot to process shuttles
Some fixes

Conflicts:
	code/game/supplyshuttle.dm
Minor shuttle fixes and cleanup

Readds the missing "shuttle has left the station" message, improves the
ETA calculation and reorganizes the procs in shuttle_controller.dm