Derive splink when registering SP, allow visible = True in SP portal
    
    The splink value wasn't being passed when registering a new client.
    We don't need to prompt for this since we know it already
    
    Accept 'True' as a value for visible when determining if we
    should show a provider on the SP portal page.
    
    https://fedorahosted.org/ipsilon/ticket/148
    
    Signed-off-by: Rob Crittenden <rcritten@redhat.com>
    Reviewed-by: Patrick Uiterwijk <puiterwijk@redhat.com>