Updated targets, Part 1/3 (ARKit)

[met4citizen]

This PR provides new versions of the ARKit targets. The main changes and issues it addresses are:

• Fixed deformations at the corners of the mouth in all ARKit mouth shape keys
• Limited the dynamic range of the eyelids, eyelashes, jaw, mouth, etc., which previously extended too far for a realistic human face
• Excluded all vertices below the neck area from all ARKit targets
• Minor fixes and improvements

Notes:

• By default, the character's mouth appears slightly low relative to the teeth, and the upper teeth do not show in most shape keys as they do in all my reference models. I did not try to compensate for this in the shape keys, as the correct fix is likely to adjust the model's mouth parameters and raise the mouth slightly. It also appears that the MPFB character's mouth is slightly open in the rest pose, whereas in all my reference models the mouth is fully closed. As a result, the corners of the mouth do not necessarily touch.
• I have a reasonable artistic eye, but my Blender/3D modeling skills are limited, so there is likely still room for improvement. Issues will probably surface as these targets are used more extensively. For example, I currently don't have a strong intuition for how these shape keys will behave when the character's age and/or facial features change significantly.

I will make separate PRs for Microsoft visemes (Part 2) and Oculus visemes (Part 3). This may probably take some time.