BibIndex: new country tokenizer, country index, country KB

* Amends SPIRES to Invenio converter to use index cc->country
* Disables SPIRES sintax conversion cc->postalcode
* Adds a BibIndexCountryTokenizer
* Adds regression tests for country tokenization on country index
* Adds countrynams-to-country.kb
* Adds country index and country field (in tabfill and with an upgrade script)

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