final balance adjustments before playtest

Jeep machinegun slightly de-buffed vs. infantry. It was a bit too effective at killing infantry.
Rockets slightly de-buffed vs. vehicles/tanks. Damage vs. wood returned to original levels. 
Flamethrower damage vs. wood returned to 100% (generally found that infantry already do high damage vs. buildings)
Guard tower dmg. vs vehicles/tanks buffed (to counter rocketbike spam)