Goal of this change is to simplify usage of the watch page feature.
It comes with important changes:
   - the watch location switches in the bell menu area have been removed
   - a new button with a logo and a status has been introduced next to edit button
   - a new modal has been introduced when clicking on the button providing various choices
   - the watch page API have been modified to not just provide boolean value watch / not watched, but to provide a larger panel of possible statuses
   - a REST resource have been provided to allow watching / blocking / removing a filter on a location
  

* Start providing REST API for watch pages to simplify operations
  * Distinguish more cases for watched / ignored pages to improve UI
  * Provide implementation for REST API for watching pages
  * Improve WatchEntitiesManager API to support more operations
  * Improve WatchedEntityReference API to use UserReference
  * Provide a dedicated page to handle watch settings
  * Start writing javascript code to handle choices
  * Fix issue in WatchedEntitiesManager
  * Start providing doc / fixing checkstyle
  * Handle a bit more actions in UI
  * Fix a bug in state computer related to the fact that the scoe filter
    hierarchy is not really a hierarchy
  * Provide a new API to allow computing the reference of the immediate
    ancestor of a page for which a filter exists
  * Improve UI to base possible actions on multiple criteria: current
    watch status, presence or not of a filter on an ancestor, and check
if the page is terminal or not
  * Encode all options for the watch settings modal
  * Change the URL scheme for the REST API
  * Minor improvments
  * Provide test for notification rest module
  * Fix checkstyle
  * Put revapi ignores
  * Start fixing since
  * Provide translations and improve UIX code
  * Provide page object and fix integration tests
  * Ensure to not display the watch status for guest
  * Fix a few since and some problems in UIX
  * Fix API of WatchedUserReference
  * Fix bad escaping
  * Better exception handling for creating references
  * Various improvments in translations (active voice + use of ignore)
  * Improve a bit the UI
  * Improve UI when a page is ignored/followed by an ancestor and check
    proper rights
  * Review available options and improve javascript to allow chaining
    operations: following space when the page is followed implies to
first unfollow the page to not keep unnecessary filters and mess up the
UI
  * Improve translations
  * Clean up some unnecessary code
  * Make the UI a bit more clear
  * Fix some stuff after rebsae
  * Slightly improve UX
  * Fix missing unstable
  * Fix bad deprecated API call