Add physics methods to queue and apply movements
Apply movement by queueing it to do later
Improve movement inertia

Handles all 3 axis. Incoming velocity is only added to inertia when
leaving the ground, and does not continually add to it.
Improve mid-air control
Some physics cleanup

Gets rid of some unneeded/unused variables, and halves the 'on ground'
offset.
Implement a jumping state
Fix tracing down
Better handle animations with a 0-length loop
Improve stepping down when starting on the ground
Implement jumping animations
Don't start the jump animation until after the actor is airborn

A bit counter-intuitive, but otherwise certain jump animations will improperly
add an offset to the initial inertia.
Add NPC landing sounds for soundgen keys