Added documentation to actor queue.
Added documentation to actor queue.

guregu/eng,EtienneBruines/engi,Newbrict/engi,ajhager/engi,mboersma/engi,EngoEngine/engo,paked/engi,guregu/engi,Newbrict/engo,wangshijin/engi,Newbrict/engi,EngoEngine/engo,Newbrict/engo