Fixes #6820

Readds missing check, makes hoverpods their own mech type and moves them
to another folder.
Fixes turbine computers disappearing when broken/out of power.
adds an ex_act to ore boxes. Explosions no longer del all the ore in a box
Fixes #6822
incorporates Zuhayr's suggestion
Cleans up hovererpod move code, adds ion trails

No need to duplicate the mecha move code when we're only interested in
drifting. The hoverpod also starts drifting when it runs out of power,
now.
Merge pull request #6830 from Glloyd/fixes

Two More Little Fixes
Merge pull request #6823 from mwerezak/hoverpod

Fixes #6820, #6822, adds ion trails to hoverpods.
Merge pull request #6855 from Baystation12/master

Master - > Freeze
Merge pull request #6856 from Baystation12/dev-freeze

Freeze - Dev
Merge remote-tracking branch 'upstream/dev' into PortaTurret