Trying to fix issue where rotation/translation by touching suddenly jumps because touch processing isn't perfect.

Two measures taken here:
1) Track the touch ID to use as the main pointer position, other touches just provide the touch count.  (Note, pinch or twist action ignored, but would be nice to add later).
2) In the case where the main touch is lost, revert back to head of touches list, probably might be a jump in rotation/translation.

There still seems to be an issue where manipulation locks up or gets stuck in one of the modes.