Arcade vehicle integration

[Loryhoof]

I'm opening this issue because I think we're in need of some new modes of transport in the engine. Currently I'm working on a physics based car, with (somewhat) realistic behavior.

Scope of the task:

• [x] Fully customizable (spring length, stiffness, damping, friction, slip etc.) without coding. (in .metaversefile or .scn file)
• [x] Able to swap out vehicle model easily and set wheel positions. (in .metaversefile or .scn file)
• [ ] Must support multiple seats. (currently max 4)
• [ ] Able to be driven by NPC

[avaer]

Must support multiple seats. (currently max 4)

This is probably the hardest part, I'd leave it to last. It also seems not strictly related to vehicles, but more generally applies to anything that's sittable.