enable space group selection in pandda.analyse tab

[tkrojer]

It is already possible to sort by space group (although I am not sure how functional the table is), but this will not help in case where the crystal forms are of the same space group, but have different unit cell volumes.
Frank's suggestion: What about using both space group and cell volume (rounded to nearest 1000) to build the labels in the drop-down? P21-3100 or P21-1200 or something?