if a link or image is an editing host (has @contenteditable=true), its body is editable *but* its attributes should not be considered editable: if the attributes come from a t-att-*, @contenteditable will be set on the node itself. such elements should be ignored by the link & image dialog handling thing, as editing their attributes has undesirable effects. bzr revid: xmo@openerp.com-20131216134424-fdqs03i9pidbmaqt