First attempt to create a '.pnm' file extension that stores a simulation
First attempt to create a '.pnm' file extension that stores a simulation


Former-commit-id: cd60d5738a93bf81bc27d899b9028776ea66f0f7
Former-commit-id: 30d127f13df6a5e346073f7b74bba3a95b58febd
TomTranter/OpenPNM,stadelmanma/OpenPNM,PMEAL/OpenPNM,amdouglas/OpenPNM,amdouglas/OpenPNM