Improved manhack and turret functionality

Stopped casings from being dumped to prevent game freeze and save bloat if turrets are extensively used (imagine the turret as having a case recycler or some such inside).

Because scrambler grenades were removed, EMP blasts now have a small chance to deactivate manhacks and turrets instead of destroy them (the player can't use them without high skill anyway).

Manhacks now have additional tactics (follow player, engage, or deactivate). They will default to engage.

Additionally, destroyed manhacks will now drop `broken_manhack`s instead of regular corpses. This new object can be disassembled for scrap parts.