Rebalance and rework emplacements

[shroobloom]

Grenade Turret:

• name "40mm HE Turret" -> "40mm Grenade Turret"
• spread 0 -> 0.15
• damage 150 -> 100
• explosion effect size now reflects the actual blast radius better
• muzzle velocity 35 -> 45

Railcannon Turret:

• made damage dropoff from the blast radius much more aggressive (internally: swapped "wide" and "tight" explosion multipliers to 0.33 and 0.66 respectively)
• damage 1188 -> 400

14mm Turret:

• name "14mm Turret" -> "Anti-Material Turret"
• explosive to bullet damage ratio 0.66:0.33 -> 0.5:0.5
• damage 260 -> 128
• spread 0.005 -> 0.01

Machinegun Turret:

• name "7.62x39mm Turret" -> "Machinegun Turret"
• firerate now ramps up overtime the longer you hold it down (3s spinup time, 6s spindown time)
• added a heat value, if this gets too high the gun stops shooting as fast and starts smoking (7s overheat time, 4s cooldown time)
• Fire interval 0.03 -> 0.0225
• Damage 37.5 -> 31.5
• (^ DPS 1250 -> 1400)
• added a firing sound akin to a minigun