Adds quadrupeds.

[MistakeNot4892]

DNM WIP opening for diff, will probably split the systems out into several PRs.

Description of changes

• Adds a category system to limbs and uses it for a generalized stance calculation that should support both bipeds and quadrupeds.
• Adds drakes as an example quadrupedal species.

Why and what will this PR improve

More flexible bodytypes.

TODO

• [x] Work out why gibbing a drake crashes the client.
• [x] Readd mouth gripper.
• [ ] Add resting/sitting state icons.
• [x] Add alt icons for backpacks.
• [ ] Restrict drakes from jobs.
• [ ] Test/fix stance code

Authorship

Myself.

Changelog

Nothing player-facing.