Menu entry to toggle thumbnails on specific directories
Followup of #78 (closed)
Like Dolphin, which has a toggle in its view-menu for that.
Could be added in the "view" menu, above, or below the zoom-levels. Behavior, if per-directory-setting is disabled:
- checking it on a local drive, sets the global one to "only local"
- checking it on a remote drive, sets the global one to "always"
- unchecking it on a local drive, sets the global one to "never"
- unchecking it on a remote drive, sets the global one to "only local"