cubicweb-relationwidget #10184462 Add entity creation + linking [validation pending]

It should be possible to create a new entity to be linked.

done in0.3.3
load left0.000
closed by#2cb003cae5ce [view] hide tab HTML markup if no creation form is wanted
patch[view] hide tab HTML markup if no creation form is wanted [applied][creation] Update table after a new entity is created [applied][creation] Add a title to selection tab [applied][creation] Refactor to ease overloading [applied][creation] Improve tab titles [applied][creation] Adapt empty rset handling [applied][creation] enlarge pop-up so that creation form fit into it [applied][creation] use different tabs to set relation / create entities [applied][creation] Use a custom creation view instead of a custom form because the form is likely to be already customized [applied][creation] Display creation form button only when current user has "add" permission on the target etype [applied][creation] Do not generate 2 iframes with the same dom id [applied][creation] Display validation error messages in the dialog [applied][creation] Customize form buttons: make "cancel" close the creation form, hide "apply" [applied][creation] Display newly created entity using its incontext view [applied][creation] Add an entity creation button in the modal window [applied]