Cleanup of GenericNetwork:  added flatten functionality to several methods, expanded doc strings
Cleanup of GenericNetwork:  added flatten functionality to several methods, expanded doc strings


Former-commit-id: 8c087d4eacfca203b70011c3069f3cc0d5722fd0
Former-commit-id: 288badaffa5e8bc452563757ebff8a4b25643209
stadelmanma/OpenPNM,amdouglas/OpenPNM,TomTranter/OpenPNM,amdouglas/OpenPNM,PMEAL/OpenPNM