dev : #110215 : more relevant search

• titles, authors, dewey, ... indexation : exact all exact labels are
  kept and indexed before phonetic. Articles are no longer dismissed
• authors indexation : in order to find "miles davis" AND "davis
  miles", authors are indexed like this: "name firstname name"
• simple search: exact expression has more relevance and passes the
  "dancing queen" test
• search by expression: users can now search an exact expression using
  double quotes. In this case, if no result found, search is not extended