Missile Combat part 9

Now I am at the point where I can test everything that is implemented(PD
is not yet implemented), and there are several bugs here:

>>> Bug: Target taskgroup was deleted, not missile group. woops. <<<
Resolution: 500    Maximum Range vs 25000 ton object (or larger):
-646,014,592 km on display screen.
preserve actions available selection when choosing new system location
available on F12 screen.

More testing will be required, and the TG bug is going to take some
doing to track down.