Fix Lua API interaction with destroyed actors

This cleans up a couple of issues with the lua bindings:
* The bindings were regenerated each time an actor was bridged into lua (oops).
* The binding state (after fixing the above) becomes inconsistent based on whether the actor is first queried before or after it is destroyed.
* Undefined behaviour occurs commands are issued to destroyed actors via the Lua API.

The bindings will now unregister all but specifically marked property groups when an actor is destroyed, and the missing property error message will now mention that the actor is dead.