Standardise schema for recording what images are available and what their quality is

[dosumis]

There are duff image files in the various image datasets we host. This can be on a per image file basis, so we might have a good registration (channel) with a bad SWC but a good NRRD.

Image types available and their quality should be recorded on in_register_with edges.

Simple strategy is just to record a list of files for each file type and leave duff ones off the list. As we have no nested data structures as attributes, recording more complicated information about images is challenging.

[dosumis]

TODO - link various image data quality tickets to this one.