ws: Don't assert when serving a zero length resource

An erroneous assertion did not take zero into account.

Closes #1249
Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
shell: Don't start plots when they have not been layouted yet

This allows the callers to be less careful when calling start().

Reviewed-by: Stef Walter <stefw@redhat.com>
shell, DockerClient: Add reconnect method

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Improve handling of Docker failures

Instead of showing an additional alert box at the top, we now hide the
main content and show only the error message.  There is a button that
will start docker.socket and then reconnect to Docker.

The failure message is also shown for the container and image details
pages.

Fixes #705
Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Offer to reconnect to Docker when appropriate

Reviewed-by: Stef Walter <stefw@redhat.com>
test: Add tests for Docker failures

Reviewed-by: Stef Walter <stefw@redhat.com>
test: Include "docker-io" in cockpit flavour

Reviewed-by: Stef Walter <stefw@redhat.com>
daemon: Remove all access control

This hasn't been the task of cockpitd since it moved to the session
bus.

Closes #1251
Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Check roles for network control

Closes #1252
Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Role checks on the dashboard

To prevent non-admins from doing things that wont work for them.

Fixes #1248
Closes #1257
Reviewed-by: Stef Walter <stefw@redhat.com>
ws: Remove non-working l10n translations.

Which is all of them. :-(

Closes #1255
Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Remove some unused CSS styles
shell: Remove some unused images

Closes #1250