Branch/tdg units

@eric79 @youngca 
Here's the first pass of getting unit icons so that they can be added to the map.
insertableUnits: { "ground": [ "INF", "INFFV", "ARMINF", "MORT", "FLDART", "PAA", "AT", "ATG", "TANK", "MECH", "WHMECH", "HMG", "LMG" ] }