VC3D - Rotate and flip surface view

[SuperOptimizer]

Purpose: this would allow for clearer inspection of the surface and/or ink predictions in VC3D.

Suggested Implementation: 'r' to rotate surface view clockwise 90 degrees, 'f' to flip surface view horizontally.

Original issue by @Bodillium: ScrollPrize/volume-cartographer#44

[hendrikschilling]

Also useful: "apply" to actually edit a segment to apply the rotation. Useful for example for steering the future interactive outgrowing using the up/down/left/right choice.