Summary:
Drop duplicate results from contact completion to return
more relevant results. This is still limited by the indexing
side as we are unable to deduplicate easily based on the email
address itself (or merge the results in some clever way).

Reviewers: #kde_pim, dfaure

Reviewed By: dfaure

Subscribers: kde-pim

Tags: #kde_pim

Differential Revision: https://phabricator.kde.org/D28615