Human: lots of updates, see commit comment
• 2 walk animations & default idle poses
• Same prefab changes as Citizen
• Now accounting for limbs being slightly twisted in bindPose unlike Citizen — this 'unbiases' the constraints so there's practically no change in the resting pose
• Added constraints that slightly pivot leg_upper_X_twist1 upwards as the leg bends; this makes the lower part of thighs 'bulge up' a bit, which complements the "poor man's RBF" kneecap constraints, and improves the look at extreme bend angles (crouching, etc.)