first pass at seagull "groups"
- groups (animators+rigs) are different than "flocks" (shader animation), flocks stay up high in the sky, groups actually land
- groups land at "interest points" which are components that can be placed in scenes/prefabs
- groups are a single entity, with multiple gulls, similar to a swarm, except they actually have hitboxes
- if you come close a group of gulls, they will startle and fly off, at a sufficient distance they turn into a "flock"
- after a wait time, the groups will come down to land at a new interest point, and transition from a flock back into a group
- individual birds can be shot while in a "group", with ragdolling corpses
- also various improvements to flock movement