web: Use bar graphs in container image overview rows

These represent the size of the image on disk.

Partially fixes #312

Signed-off-by: Marius Vollmer <mvollmer@redhat.com>
web: Added cockpit_get_dbus_client function.

To allow multi-machine aware pages to do the right thing.

Reviewed-by: Stef Walter <stefw@redhat.com>
web: Memory usage bar graphs in container overview rows

Partially fixes #312

Reviewed-by: Stef Walter <stefw@redhat.com>
web: Add CPU column to container overview.

Closes #316
Fixes #312

Reviewed-by: Stef Walter <stefw@redhat.com>
web: Display 'play' buttons next to images to run a container

These buttons don't do anything yet.

Got the column smaller by setting a fixed width on td.cell-buttons.
Not completetly happy with that, but perhaps there's not a better way.

Work on issue #301
web: Run images from the docker overview page

Bring up the run dialog by pressing the play button.

We no longer need to refresh the image information, as we have relevant
information being updated by the docker DOM code.

Work on fix for issue #301
web: Implement DockerClient.start() .stop() .restart()

Since we want to be able to call these from the overview page
in addition to the details page.

Part of issue #301
web: Start and stop containers with buttons on the overview page

Part of fix for issue #301
web: As containers are starting/stopping on overview page show waiting

Show a throbber as containers on the overview page are starting
or stopping.

Along with previous commits this, fixes #301, closes #317