CAS would never be planned for turn 0 because there were no enemy ground
units, so a breakthrough attack was planned and CAS was considered
unnecessary. Fix that by rejecting all frontline stance tasks when there
are no *friendly* ground units to command.
Another issue is that CAS missions were being planned even when there
were no enemy front line forces. Skip planning in that case except on
turn 0 since we expect there to be enemy ground units on turn 1.
Fixes https://github.com/dcs-liberation/dcs_liberation/issues/1629
This makes it so that the mission planning effects are applied only if
the package can be fulfilled. For example, breakthrough will be used
only if all the BAI missions were fulfilled, not if they will *attempt*
to be fulfilled.
This improves the AI behavior by choosing the stances non-randomly:
* Breakthrough will be used if the base is expected to be capturable and
the coalition outnumbers the enemy by 20%.
* Elimination will be used if the coalition has at least as many units
as the enemy.
* Defensive will be used if the coalition has at least half as many
units as the enemy.
* Retreat will be used if the coalition is significantly outnumbers.
This also exposes the option to the player.
