shell: Handle modern DBusClient in hostname_for_display

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Simplify HTML

Mostly, move the top navbar out of #content.

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Host switcher

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Hide navigation when showing the dashboard

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Ensure that the plots resize when the host switcher toggles

Closes #1409
Reviewed-by: Stef Walter <stefw@redhat.com>