This is a blend of the previous 'sitting' and 'standing' HMD modes.
Basically, when you move your head within a small range (20cm) your
avatar will lean appropriately, however when you cross that threshold
your body will move underneath you, re-centering your head above the body.
While this occurs the avatar should play the appropriate walking animations.
using its filename and texdir properties (as Faceshift does) to locate the
corresponding model. Also fixed a bug with the fallback models (they were
invisible after second failure).
