ContainerStack 0.4.1

Starting and stopping containers works again on a machine where another Docker
bridge got there first, and one slow container no longer freezes the rest.

Fixed

• Another program listening on the Docker socket is now named instead of adopted.
  A bridge from a different build answers every status check while start and stop
  hang - measured past 150 seconds against a container the bundled bridge started
  in 2 - so the app reported a healthy engine while nothing could be controlled.
  It now says which socket is held and what to do, keeps saying it while it is
  true, and stops offering the actions that cannot succeed. Listing containers and
  reading their logs keep working, since that is what you need at that point.
• Acting on one container no longer disables every other one. Stopping can take
  the full two-minute timeout, and for that whole time no other container could be
  started, stopped, deleted or have its logs opened - and a click on a different
  container did nothing at all, without a word.
• Quitting no longer leaves runtime commands running. A command the app was
  waiting on used to survive the app that started it: eight of them were found on
  one machine, the oldest four days old, each wedged and invisible. The Docker
  bridge is unaffected and still outlives the app on purpose.