Multiple improvements to UV Cylinder and UV Sphere projection including:
* New option "Pinch" or "Fan" to improve unwrap of faces at the poles.
* Support for "Polar ZY" option on "View On Equator" and "Align To Object"
* Better handling of inputs with round-off error.
* Improved handling of faces touching the unit square border.
* Improved handling of very wide quads spanning the right hand border.
* Improved accuracy near to (0, 0).
* Code cleanup and simplification.
Differential Revision: https://developer.blender.org/D16869
280502e630