shell: Export hosts model and make it more useful

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Keep hosts sorted in the switcher

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Reconnection dialog for hosts

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Add shell.plot function

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: New (incomplete) multi-server dashboard

Closes #1455
Reviewed-by: Stef Walter <stefw@redhat.com>