Mugglify the CIF Importer

[trisyoungs]

Describe the feature / issue
Our CIF import currently revolves around a wizard, which is fine, and provides a nice separation between steps of the CIF processing that we do, but for larger crystals or "bespoke" cases containing a lot of raw atoms and no symmetry elements it is painfully slow. This is because we repeat the whole processing of the CIF at each stage of the wizard, even if nothing has changed.

The proposal here is to create a single-window import dialog, with adjustment controls on the left (e.g. bonding, moiety removal), a viewer in the centre, and output options / data (e.g. cell size) on the right. This would also preclude the need to maintain configurations for each stage in the CIFHandler class.

[trisyoungs]

Cell size / density / atom and molecule counts can go in a top bar above the viewer, analogous to the Configuration viewer.