shell: New layout for navigation.
shell: Adapt update_global_nav to new layout.
shell: Move system information code to server page.
shell: Remove "Rescue Terminal" option from dashbord menu.
shell: Highlight active navigation tab.
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.
test: Adapt check-shutdown-restart