Make dogtag an optional (and default un-) installed component in a replica.
    
    A dogtag replica file is created as usual. When the replica is installed
    dogtag is optional and not installed by default. Adding the --setup-ca
    option will configure it when the replica is installed.
    
    A new tool ipa-ca-install will configure dogtag if it wasn't configured
    when the replica was initially installed.
    
    This moves a fair bit of code out of ipa-replica-install into
    installutils and cainstance to avoid duplication.
    
    https://fedorahosted.org/freeipa/ticket/1251