Blender Git Loki

Curves: Allow caps for all geometry types

I think this wasn't allowed before because the section of a curve was
built in multiple parts. But since rBe34d3e32dda7, the whole slice
of a curve is built in one piece, so we can easily support curve
caps for all geometry types, including the new custom profile option.

Note that this also allows "caps" when the fill type is not full.
They could easily be disabled by checking for "Full" fill type
if that was preferred in the future.

See the patch for images.

Differential Revision: https://developer.blender.org/D8911