Allow VisualEditor users to set if a page whether a Disambiguation

Depends on I78dd68ff in VisualEditor (merged as of 1.24wmf7).

Bug: 61073
Change-Id: Ic13e6d9ffe5035a2672858bd7a7e54a4dff42883
Merge "Allow VisualEditor users to set if a page whether a Disambiguation"