test: Run TestDashboard.testBasic as "admin"

This just works.

Closes #1496
Reviewed-by: Stef Walter <stefw@redhat.com>
bridge: Allow both 'ready' and 'close' to be done later for a channel

We might have queued messages before the close comes and we should
process them first.

Closes #1497
Reviewed-by: Stef Walter <stefw@redhat.com>
common: Pass payload to CockpitTransport "control" signal handlers

That way they don't have to reserialize if they want to forward
a message.

Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
common: Add cockpit_pipe_transport_get_pipe() function

Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
ws: The "logout" message is forwarded

We forward the logout message from the web service to the various
session bridges.

Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
bridge: Implement "superuser" channel option

When this is set to true we use pkexec to launch another cockpit-bridge
as root, and run the channel via that bridge.

Closes #1493
Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
daemon: Also store name, color, and avatar in dashboard configuration.
shell: Update shell.hosts to new dashboard configuration storage.

This takes color and avatar directly from the dashboard configuration,
and uses the name in the dashboard configuration as a cache for the
pretty name of the target host.

Also allow setting of the pretty name via shell.hosts.
shell: New shell.image_editor.
shell: Server appearance edit dialog for dashboard.
shell: Styling for multi-server dashboard list
daemon: Remove support for local avatars.
shell: Fix to make text not overflow the buttons in the hosts list