v0.4.0

Added

• Mark rows and delete them together. In Images, Volumes and Networks, Space marks
  a row and a every row the filter shows; d then deletes all marked rows, skipping
  any in use, and Esc clears the marks.
• Clean up volumes in one go. D deletes every dangling, orphaned or unused volume
  among the rows shown, listing how many of each there are and the space they take before
  you pick.
• Abandoned anonymous volumes are marked. One that no container mounts reads
  ○ dangling instead of ○ unused: with no name to ask for it by, nothing will mount
  it again.