As a user I want to be able to get only the best rank statements of an item when reading it.
Acceptance criteria:
- A user can request to get only best statements of an item as an additional field in the query
- The field is called 'bestStatements' and will have the same type as the 'statements' field
More information on statement ranking can be found here: https://www.wikidata.org/wiki/Help:Ranking
