The previous flight plan only makes sense if the convoy will make it a
significant distance from its starting point. At road speeds over the
typical mission duration this is not true, so we can actually plan this
as if it was a strike mission near the origin point and that's close
enough.
There's some cleanup work to do here that I've added todos for.
Fixes https://github.com/Khopa/dcs_liberation/issues/996
This currently is only supported for player flights. I have no idea how
to create an AI flight plan that won't just get them killed. AI-only BAI
missions against supply routes will warn the player on mission creation.
A CP with a factory would be able to supply itself, but was not in a
supply route if it was the only connected friendly CP. When the player
starts with only one base against an enemy base this meant that it was
in no supply route, causing it to not be a recruitment location or a
place to buy more than a reserve of vehicles automatically.
