(bug 44538) add/removeListItem functions for wb.listview plus related events

* Introduces 'addlistitem', 'listitemadded', 'removelistitem' and 'listitemremoved' events to
  jQuery.wikibase.listview
* listview.enterNewListItem() will now use the new functions and therefore trigger above events
* Comes with a fix in the referenceview where .value() would in some situations return a wb.Claim
  instead of a wb.Reference item.

- patch set 2: spelling errors

Change-Id: I48b0647fa3972059ff27bf4f222613cf5f3bb17f
Merge "(bug 44538) add/removeListItem functions for wb.listview plus related events"