shell: New layout for navigation

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Adapt update_global_nav to new layout

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Move system information code to server page

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Remove "Rescue Terminal" option from dashbord menu

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Highlight active navigation tab

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Save space on the server dashboard

By using the hostname and realms directly as the label of buttons for
changing them.  Also, always leave a realm via a dialog.

Closes #1369
Reviewed-by: Stef Walter <stefw@redhat.com>
test: Adapt check-shutdown-restart

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