Websearch: SPIRES to Invenio keyword translation

* Edits _SPIRES_TO_INVENIO_KEYWORDS_MATCHINGS and
  _INVENIO_KEYWORDS_FOR_SPIRES_PHRASE_SEARCHES in
  search_engine_parser.py

* Adds unit tests for the new mappings

* Adds new 'address' field and relative tag mapping (in tabfill and
  with a new upgrade script)

* Adds new 'note' field and relative tag mapping (in tabfill and with
  a new upgrade script)

Signed-off-by: Federico Poli <federico.poli@cern.ch>
Merge pull request #35 from fpoli/prod-websearch-spires-to-invenio

Websearch: SPIRES to Invenio keyword translation
BibIndex: new `datasource` field and `786__w` tag

* Adds field `datasource`, associated with the new tag `786__w`

* Adds upgrade script

* Adds bibfield definition of `datasource` in `atlantis.cfg`

Signed-off-by: Federico Poli <federico.poli@cern.ch>