public void addCrumb(@NonNull Breadcrumb crumb){
  addCrumb(crumb,crumbs.isEmpty());
}

public void addCrumb ( @ NonNull Breadcrumb crumb ) { addCrumb ( crumb , crumbs . isEmpty ( ) ) ; }
add a crumb to this layout . the crumb will be added at the end of the list . if this is the first crumb to be added it will become the selected crumb .
