Use the CKEditor link dialog picker for choosing the home page in the wiki descriptor admin UI

Right now non-terminal page reference appear using their technical form (including WebHome). We should hide "WebHome" both when selecting from the auto-suggest and when displaying the selected page. Similar to what we do with the doc tree.

An example to test this is when changing the home page in the wiki descriptor in the admin.

IMO a better UI would be to display the tree widget when clicking in the field so that the user can choose the page by: navigating in the tree or use the finder feature of the tree. Ideally I'd also like that the tree widget have 2 tabs, one for the tree and another one for searching so that the user could also do a SOLR search to search for a page containing something.