Draft: Group CCVs by their conditions and maybe by time

Common problem: comparing different CCVs for a given PDU doesn't make sense if their operating conditions differ wildly. Am working on filtering by condition. Sometimes, we may also want to group CCVs from different PDUs generated at the same time. I don't believe the metadata we get tells us anything about the calibration job / source data which created a particular constant, so am going by heuristic of "close in time".

Also, added sliders to set vmin and vmax for plt.imshow. Sort of disappointing that plotly doesn't expose configurability in the widget.