WebSearch: new Journal Hint Service

* Adds the Journal Hint Service, that displays
  'Were you looking for a journal reference? Try: [link]'
  when the user search for a raw journal reference.

* Adds unit and regression tests for the new search service.

* Adds two unit tests to `search_from_reference`, just to be sure that
  it accepts unicode

Signed-off-by: Federico Poli <federico.poli@cern.ch>
1: D400 First line should end with '.', not 'e'
4: I102 copyright year is outdated, expected 2014 but got 2013
34:36: E126 continuation line over-indented for hanging indent
37:1: F999 redefinition of unused 'identify_ibids' from line 33
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