changes:
Lists are no longer created every time a movable moves (!)
Lists are no longer created every time a datum is destroyed (!)
Observation events now properly clean up references.
Removed the unused task_triggered event.
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.
Now limits moved registrations to when strictly necessary. That is:
* When entering a movable atom, the entering object only registers to its moved event if it has moved listeners on its own.
* Instead, when registering to a moved event, registrations occur recursively until a non-/atom/movable is encountered or a prior movement registration from the same object is reached.
Corrects a number of places where New() did not call ..(), and implements similar changes to attempt to ensure New()/initialize() complete running before qdel() runs.
Cuts down on the number of created items during server start.
