[FR] Flags in FRED's Ship editor to guardian subsystems.

A ship flag that could be ticked for each generic subsystem in the "Additional ship properties" tab in the ship editor in fred, Similar to how ship guardian can be applied as a flag, rough concept image provided:

. . .

(note lower right corner,) (location in the Additional ship properties of new features is shown as example only, it can be put wherever.)

The flag would work much like ship guardian, it would set subsystems as guardianed with a default threshold of 1, and it would apply to future ships in wings, and could be added/removed via `alter-ship-flag`

The flag would apply to `` when "Engines" is checked.

in the case that a ship does not have one of the listed generic subsystems, the checkbox could be greyed-out, and/or the flag would not apply.