Function File: [emesh,snodes,ssides,striangles] = msh3e_surface_mesh(mesh,nsrf,nsides)

Extract the plane surface nsrf delimited by nsides from mesh.

Return the vector snodes containing the references to input mesh nodes (field mesh.p), the vector ssides containing the references to input mesh side (field mesh.s) and the vector striangles containing the references to input mesh side edges (field mesh.e).

WARNING: the suface MUST be ortogonal to either X, Y or Z axis. This should be changed to account for generic 2D surface.