Fix mean curvature with correct dihedral angle 1. The last version is over simplified which does not consider the face    orientation. It leads to a non-negative curvature that is wrong. 2. Now the dihedral angle has fully taken the face orientation into    consideration.[right hand rule]
Fix mean curvature with correct dihedral angle
1. The last version is over simplified which does not consider the face
   orientation. It leads to a non-negative curvature that is wrong.
2. Now the dihedral angle has fully taken the face orientation into
   consideration.[right hand rule]

compas-dev/compas