EMI: Reduce jerkyness of animations

Most of the improvement comes from changing interpVal for the translation case.

    (_time - curBone._translations[keyfIdx]._time) / timeDelta;

to

    (curBone._translations[keyfIdx]._time - _time) / timeDelta;


This also should make interpolation between the last and first frames work correctly.


This issue has been bugging me for almost two years now. Not sure why I didn't fix it sooner...


It's still a bit jerky in some cases though. Not nearly as much though.