user: add object plugin for user_status
    
    Change user_status from a method of user to a method of a new userstatus
    class, which defines the extra attributes returned by user_status.
    
    This fixes user_status CLI output.
    
    https://fedorahosted.org/freeipa/ticket/4739
    
    Reviewed-By: David Kupka <dkupka@redhat.com>