Added a method to Core that allows for gathering of all data values assigned to a given pore(s).  This might be better of as added functionality to 'props', then it would be consistent with labels.
Added a method to Core that allows for gathering of all data values assigned to a given pore(s).  This might be better of as added functionality to 'props', then it would be consistent with labels.

PMEAL/OpenPNM,TomTranter/OpenPNM,stadelmanma/OpenPNM