The default loadout is now displayed whenever the custom loadout checkbox is unchecked.
The custom loadout is reset when the custom loadout is checked, to force the user to be prescriptive about the loadout.
Contributes-to: Khopa/dcs_liberation#725
Follow up work:
* Data entry. I plan to do the air-to-air missiles in the near term. I
covered some variants of the AIM-120, AIM-7, and AIM-9 here, but there
are variants of those weapons for each mounting rack that need to be
done still, as well as all the non-US weapons.
* Arbitrary start dates.
https://github.com/Khopa/dcs_liberation/issues/490
