Support garrisoned enitites defined in map files.
This is adding support to handle garrisoned entities defined in map files by game engine and atlas allowing future extension for atlas ui and solving recreation of entites on init in D1958. Also solving deepfreeze described in D2562.
Differential Revision; https://code.wildfiregames.com/D2597 Ticket: #3008 Patch by: Freagarach Comments by: elexis
