This fixes a number of issues with formations:
- Gives the controller an obstruction. This fixes the bug where units in formations can't gather from a tree.
- Stop special-casing formation members in PathResult. This fixes formation members being stuck in-place when they run in an obstruction.
- Makes sure units stay in Formation.IDle when they are idle so that D1337/D1901 can work their magic.
- Warn if animals enter this state.
- make sure that formation members that end up in INDIVIDUAL.IDLE go back to FORMATION.IDLE.
This fixes formation behaviour from what I can notice. Still need a general fix for "facing the destination" but I intend for that to come later.