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.
Out of curiosity, aren't all faces at the boundary always in standard orientation? (I should know this, since I implemented it, but it's been 10 years...)