User life cycle: new stageuser commands del/mod/find/show
    
    Add plugin commands to stageuser plugin:
    	stageuser_del
    	stageuser_mod
    	stageuser_find
    	stageuser_show
    
    https://fedorahosted.org/freeipa/ticket/3813
    
    Reviewed-By: David Kupka <dkupka@redhat.com>