Blender Git Loki

Fix T62815: Camera frame shift issue + stereo frame working

While I broke the non-stereo camera frame in rBf1fef41863b I came to
realize after further tests that the stereo camera frame was NEVER
correct.

It is now, regardless of the camera shift, the camera pivot, if you are
looking through the left, right or stereo eyes.

In the end all that was missing was to multiply the shift we needed to
offset the frame, by the frame width.

I also took the opportunity to perform some cleanup/refactor regarding
names. It was too confusing even for me.

Note: Non-uniformally scaled cameras still draw slightly wrong.