Reference Provider: Return only cq:Page nodes, handle collection items correctly

the reference provider introduced in needs some improvements:

• it should not return just any resource as reference, but only AEM pages. if it returns only a resource this may create problems, does not work correctly when deleting this.
  finding only a resource may happen if:

  • the AEM page persistence strategy is not active

  • a configuration collection is used (this should be fixed with )

  • "legacy" configuration content exists that was not stored with the AEM page persistence strategy

• in case of configuration collection it should not only return the root page (once this is a page, see ), but also the child pages (=collection items)
  for the collection items the item name should be added to the reference name

• if only a resource is found we should try to get a containing page

  • different persistence strategies may may use different scopes for defining the page

  • if we found a containing page we return this as reference

  • but only if it's not the same page that was activated initially (this may happen if the tools config page persistence strategy is used)

• we need unit tests for these different scenarios