Contacts: Don't display duplicate numbers

* Currently the db stores the same number in various formats and the
  adapter shows each of them
* Manually filter the results before swapping the cursor with a new
  one where we explicitly skipped the duplicates

Co-authored-by: Luca Stefani <luca.stefani.ge1@gmail.com>
Change-Id: I5cc4e108a7ba308f8293edcae19360969a77b505