Allow SP registration from ipsilon-client-install
    
    This optionally allows a SAML SP to be registered with the IDP when
    running ipsilon-client-install.  To register an SP, the following
    options are used:
    
      --saml-idp-url   (Ipsilon IDP URL)
      --saml-sp-name   (Name to register the SP as)
      --admin-user     (Ipsilon admin user)
      --admin-password (Ipsilon admin password file)
    
    If the --saml-idp-url option is set, we attempt to register the SP.
    The --saml-sp-name option is required if you are registering a SP.
    The --admin-user already defaults to admin, so it only needs to be
    specified if your admin user has a different username.  If the
    --admin-password option is not specified, we prompt for the password.
    
    The --saml-idp-metadata was previously required, but this option is
    redundant if the new --saml-idp-url option is specified and you are
    not using a local copy of the IDP metadata.  You can now just use
    the --saml-idp-url option, and we build the metadata URL from it.
    This helps to minimize the number of required options when you are
    registering an SP during installation.
    
    https://fedorahosted.org/ipsilon/ticket/101
    
    Signed-off-by: Nathan Kinder <nkinder@redhat.com>
    Reviewed-by: Rob Crittenden <rcritten@redhat.com>