Add a helper for finding the map edge in a given direction.
Support CenterPositionInit for Aircraft.
Don't crash if trying to check targets outside the map.
Add squad and quantisation support to AirstrikePower.
CarpetBomb -> AttackBomber.
Fix GravityBomb explosion position.
Change the C&C Airstrike to be more support than sniper.

Slight buff to total damage dealt, but no longer 1-shots buildings.
Add contrails to C17 too.
Add strafing to C&C airstrike.
Merge pull request #4036 from pchote/aircraft-polish

C&C aircraft polish.
separate Rank effect from GainsExperience

fixes #3957
StyleCop clean