Missile Combat part 5, MFC track checking

OrdnanceTargetTN was moved to just TargetTN, the plan there is to
eventually move BFCs to use TargetTN rather than just explicitly having
a ship target.

MFC tracking is now checked, next up, plugging missiles into the sensor
model. MFCs can lose tracking for moving out of range, the target moving
out of range, the MFC being destroyed, or the target being switched.