Math: Less mormalization error in Quaternion.slerp.

Animation: Interpolants & extensibility overhaul.

Ignore empty entries in MTL files

add 3MF Loader

Removed unnecessary touchZoomDistance resets

The `_touchZoomDistanceStart` and `_touchZoomDistanceEnd` resets are not needed since the values will be set in the `touchstart` function when two or more touches are present.

Fix bower.json ignores

Multitouch fixes

* Removed unnecessary `default` case for two or more touches on `touchend` to prevent issues with 3 or more touches.
* Reset zoom distances on `case 0` and `case 1`. I couldn't combine them easily without doing a separate `if` statement.
* Simplified `case 1` action to set `_moveCurr` and `_movePrev` to the current touch position preventing camera jumping next time `touchmove` is called.

Related to issue #7185 and pull request #7406

Revert this one for porting dependent code.

Blender export bugfixes