Zeroth order version of SampleSet
Zeroth order version of SampleSet

Untested, probably full of problems. But I hope this is enough that JHP can
add storage support.

openpathsampling/openpathsampling,dwhswenson/openpathsampling,jhprinz/openpathsampling,jhprinz/openpathsampling,choderalab/openpathsampling,dwhswenson/openpathsampling,openpathsampling/openpathsampling,choderalab/openpathsampling,openpathsampling/openpathsampling,choderalab/openpathsampling,jhprinz/openpathsampling,dwhswenson/openpathsampling,openpathsampling/openpathsampling,dwhswenson/openpathsampling