Buff tank guns, esp. vs. buildings

Tanks are a bit underwhelming in their ability to take down turrets and buildings during an attack. Their ROF has been upped, and their damage vs. wood has been increased.

Their damage % vs. infantry has been lowered to keep it the same DPS. 

Light tank bullet speed reduced a bit to make it possible to miss. It's now the same speed as the turret, and still faster than MTNK/HTNK's bullets.