Makes events global.

Greatly decreases the number of objects that need to be created (currently 3 event handlers in total vs basically 3 per datum)
The price is a slower lookup of listeners but on a per round basis it should still be much less than the current startup time penalty.

code/datums/observation/_debug.dm

@@ -0,0 +1,11 @@
+/****************
+* Debug Support *
+****************/
+var/datum/all_observable_events/all_observable_events = new()
+
+/datum/all_observable_events
+	var/list/events
+
+/datum/all_observable_events/New()
+	events = list()
+	..()