Fix project bv curl conf

Hi,

Here's a new function to handle the Dirichlet boundary conditions for FE_Nedelec elements. It uses a fairly simple L2-projection method to compute the degrees of freedom on edges and faces. Rather than replace the current function, I've given it a new name as this may be less efficient on geometries with rectangular faces.

This also doesn't solve the issue when the face orientations are not of standard type.
I haven't checked, but I'd assumed this was the reason for the sphere geometry failing to work as expected. It's possible the face orientations on the interiors are to blame instead.