Steal things from pyCHX

Originally noticed in https://github.com/NSLS-II/ptycho_gui/issues/10#issuecomment-505265135. Since there is a retirement plan under discussion for [NSLS-II-CHX/pyCHX](https://github.com/NSLS-II-CHX/pyCHX), it'd be nice to steal useful things from it and incorporate into our codebase, provided that CHX is still interested in ptychography experiments. 