New method Added to Fickian diffusion algorithm for cubic networks
New method Added to Fickian diffusion algorithm for cubic networks

It calculates effective diffusivity in any direction which user wants
and if the user does not send any specific direction, it will return the
values of all directions.


Former-commit-id: 6a23434a5c087c5fce9e58332621a6b7be014b2b
Former-commit-id: 5857d208baa62774fb485fa76774ec11bcf1cd0f
TomTranter/OpenPNM,amdouglas/OpenPNM,amdouglas/OpenPNM,PMEAL/OpenPNM,stadelmanma/OpenPNM