Alternative booster separation condition

[Patrykz94]

For missions where we can't afford a boostback burn (usually GTO missions), it needs to be possible for the booster to separate when it's predicted impact point crosses the ASDS position and not just when it reaches a certain DeltaV level.

Those missions will require adding the launchAzimuth setting in PEGAS mission file to make sure that the booster flies directly over the ship. It might also require changing the launchAzimuth in flight to correct for any error gained along the way.