Some simplifications (potential simplifications, mainly in the form of commented-out code, while units tests are being built) in code calculating diffusivity in spherical-polar coordinates and then changing basis to Cartesian coordinates.
Some simplifications (potential simplifications, mainly in the form of commented-out code, while units tests are being built) in code calculating diffusivity in spherical-polar coordinates and then changing basis to Cartesian coordinates.

rjferrier/fluidity,iakovos-panourgias/fluidity,rjferrier/fluidity,jjo31/ATHAM-Fluidity,iakovos-panourgias/fluidity,rjferrier/fluidity,jrper/fluidity,jjo31/ATHAM-Fluidity,iakovos-panourgias/fluidity,jrper/fluidity,jjo31/ATHAM-Fluidity,rjferrier/fluidity,iakovos-panourgias/fluidity,jjo31/ATHAM-Fluidity,jrper/fluidity,jrper/fluidity,iakovos-panourgias/fluidity,jjo31/ATHAM-Fluidity,jrper/fluidity,rjferrier/fluidity