Stress cleanup
Cleanup of the stress.f90 routine. Stress with GGA in the noncolinear case should work now, but it is still untested: do not trust the added tests. Stress for meta-GGA in the LSDA case is not yet implemented.
Cleanup of the stress.f90 routine. Stress with GGA in the noncolinear case should work now, but it is still untested: do not trust the added tests. Stress for meta-GGA in the LSDA case is not yet implemented.