Added a trait that removes an actor when prereqs are met, with delay.

It is quite useful if you want a switch upgrade.
An example would be to upgrade rifleman to use bazookas, that unlocks an upgrade to revert them back to rifles, when that is researched it kills the actor that had the other prereqs so you don`t have both at once.

Its also quite funny to see all your powerplants explode when you build a barracks.
Personally I'd rather just include ```ITick``` and do the tick countdown here.
I'm also not sure what will ```DelayAction(info.CheckDelay, ...``` do if you have a CheckDelay of 0, and remove the actor in the AddedToWorld call. I suspect it will attempt to remove the already removed actor a tick later.