docs: Add yet another libvirt based app
    
    As announced on the list [1], Cherrypop is a management
    application based on libvirt. It's a decentralized cloud software
    with nice scaling ability.
    
    1: https://www.redhat.com/archives/libvir-list/2015-September/msg00670.html
    
    Signed-off-by: Michal Privoznik <mprivozn@redhat.com>