Added Unit class.

Included some fields, needs methods.
Merge remote-tracking branch 'justin/master'
Merge remote-tracking branch 'Sam/master'
Merge remote-tracking branch 'Justin/master'
Added Interfaces
-Attackable
-CanAttack
-CanTransport
-Movable
Merge remote-tracking branch 'Austin/master'
Merged Team Changes
Merged changes created by team. Also corrected a few identifier issues
with Structures and Turrent classes. Also started Interactable class
Changed Structures to Stucture
Merge remote-tracking branch 'Dan/master'
Merged with Dan
added Garrison class