Refactor NURBS

[IdoAkkerman]

After quite some added features there seems a growing need to refactor the existing NURBS code base, particularly NURBSExtension.

I am staring this discussion to get input on what is important, what is in the pipeline.
And how knows (or can help with) what ?
Here are some ideas from my side:

0 Are all the current features sufficiently covered in unit tests and/or nurbs miniapps?

1 Move/remove certain data members, to minimize duplicates and create more clarity.

• Remove the tables from NURBSExtension
• Move the activeXXX from NURBSExtension to ParNURBSExtension
• Remove Knotvector and order from NURBSExtension ( Knotvectors resides in Patch & Order resides in KnotVector)

2 Rationalize member signatures. Partly to accommodate the above.

3 Make sure the base class NURBSExtension, can be easily extended

• NCNURBSExtension: To accommodate nonconforming topologies and patches
• VNURBSExtension: To enable multipatch vectorvalued NURBS-based finite elements
• Parallel implementations of the above.