Support for BasisCurves

[virokannas]

It would be great if there was support for BasisCurves - don't know if that's currently a limitation of embree or ospray, but still, would be great.

[carsonbrownlee]

embree supports Bézier, B-spline, and Hermite curves. We plan on first putting in subdivision surfaces, which we recently added to OSPRay, and curve support will follow that effort. If want to undertake this before that, it shouldn't be too hard to put in as we already have curve support in OSPRay.