Like with deleting waypoints, these will degrade the flight plan to the
2.1 behavior.
Ascend/descend points aren't in use any more, so I removed those.
`FrontLine` is tightly coupled with `ConflictTheater`.
Moved into the same module to prevent circular imports.
Moved `ConflictTheater.frontline_data` from class var
to instance var to allow save games to have different
versions of frontlines.
Previously we were trying to make every potential flight plan look
just like a strike mission's flight plan. This led to a lot of special
case behavior in several places that was causing us to misplan TOTs.
I've reorganized this such that there's now an explicit `FlightPlan`
class, and any specialized behavior is handled by the subclasses.
I've also taken the opportunity to alter the behavior of CAS and
front-line CAP missions. These no longer involve the usual formation
waypoints. Instead the CAP will aim to be on station at the time that
the CAS mission reaches its ingress point, and leave at its egress
time. Both flights fly directly to the point with a start time
configured for a rendezvous.
It might be worth adding hold points back to every flight plan just to
ensure that non-formation flights don't end up with a very low speed
enroute to the target if they perform ground ops quicker than
expected.
Make the type of the waypoint a non-optional part of the constructor.
Every waypoint needs a type, and there's no good default (the previous
default, `TAKEOFF`, is actually unused). All of the target waypoints
were mistakenly being set as `TAKEOFF`, so I've fixed that in the
process.
Also, fix the bug where only the last custom target of a SEAD
objective was being added to the waypoint list because the append was
scoped incorrectly.
