Simplify HeliFly interface.
Add range support to HeliFly.
Simplify Fly interface.
Add range support to Fly.
Ensure that planes circle after being ordered via IMove.
Add self parameter to Attack activity actor.
Add MinRange plumbing to attack activities.
Add MoveAdjacentTo overload for moving within a range.
Use MoveAdjacentTo for attack activities.

Fixes #2104. Fixes #2923. Fixes #4455.
WIP: Add Guard to aircraft.

TODO: Need the FlyAdjacentTo activities before this will work.
DEBUG: Add guard and auto target to ra aircraft