Show labels on on entities

Currently a widget is shown whenever a npc speaks, but we want to expand that to allow for always show a label on entities of certain types. When a npc speaks this label should be expanded to show the current speak widget.
This should be done by keeping a pool of already created windows (unlike the current system which creates them from scratch every time).
We should also mark those entities that are currently possessed by another user (through the external attribute).