RFE: add `fs sets --without-images` to `admin cleanse`

[joshmoore]

see: https://forum.image.sc/t/ghost-files-taking-storage-space-in-omero/48029/6

omero admin cleanse could (by default or optionally) find imported filesets which have no associated images. Such filesets are almost always the result of a failed import, and the only recourse users have to remove them is to find them with omero fs sets (or an HQL query) and delete them manually from the CLI.

[imagesc-bot]

This issue has been mentioned on Image.sc Forum. There might be relevant details there:

https://forum.image.sc/t/ghost-files-taking-storage-space-in-omero/48029/7