Wikidata description under page title.

- Created a more centralized cache of Wikidata descriptions, mapped to
  q-numbers, and accessible from other classes.
- Updated the full-text search fragment to make use of this cache.
- Added description text under page title in lead image view.
- Added a nice animation to the page title when the description becomes
  available.

Change-Id: I8136bd9a358231884e1e47b027f4ad6e95609570