Hoverpod tweaks

Hoverpods are a subtype of mecha/working again, but drills are now
ripley specific. Hoverpods have increased cargo and can carry 3 tools.
Hoverpod crates now come with a clamp and passenger compartment
pre-installed.
Brings back the combatpod, can equip weapons.
Factors out common mecha/working procs

Refactors a bunch of identical hoverpod and ripley procs and moves them
into mecha/working
Allows toggling hoverpod stabilization
Merge pull request #6857 from mwerezak/hoverpod

Hoverpod tweaks and mecha/working code cleanup