fix #3598 ("vibrating" units)

make calls to script->{Start, Stop}Moving more consistent: only run them
when a unit transitions from zero to non-zero speed or vice versa, and no
longer do so during in-place rotations

(especially that last part might break a few animations, so please test)
s/30/GAME_SPEED in a few places

! remove TA-specific code in CobInstance::Create
(NOTE: this changes the argument value to COB's SetMaxReloadTime
for units equipped with BeamLasers and/or more than one weapon!)