Update weapons.yaml

After playtesting, general sense was that guard towers should be buffed and not be easily outranged or quickly killed.
The Rocket Bike is revealed to be OP. It gets hit with the nerf bat; back to previous levels. Burstdelay introduced.
Guard tower range increased 5 -> 6.
Adv. Guard Tower range increased 7 -> 8.
TowerMissle buff vs. vehicles, nerf vs. infantry 
Flamethrower vs. wood reduced 200% -> 150%.
Grenade speed increased 8 -> 12. May increase further.  
All turrets do less damage vs. wood, to discourage basewalking.