Make Elasticsearch STARTSWITH behave like in VCS for non ecm:path field

When using STARTSWITH operator on a hierarchical vocabulary the searched root term must be matched.

For example, if a document has dc:coverage value to Europe/France, the query below will not match the document using Elasticsearch, while it does using VCS:

SELECT * FROM Document WHERE dc:coverage STARTSWITH 'Europe/France'

Note that when using STARTSWITH with the special ecm:path field, the expected behaviour is different, VCS and ES does not return document that match the root term.