textutils: translate_to_ascii() unknown chars fix

* translate_to_ascii() checks the characters one by one in order to
  make sure unrecognized values are ignored ("" instead of
  printing "[?]").  (closes #1754)

* Adds unit test for this case.

Signed-off-by: Federico Poli <federico.poli@cern.ch>
Tested-by: Jan Aage Lavik <jan.age.lavik@cern.ch>
Reviewed-by: Tibor Simko <tibor.simko@cern.ch>
WebSearch: faster collection children cache

* Improves performace for collection children cache
  by minimizing the number of database calls.  (closes #1739)

Signed-off-by: Ludmila Marian <ludmila.marian@gmail.com>
Reviewed-by: Tibor Simko <tibor.simko@cern.ch>
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 BibIndexCountryTokenizer
* Adds regression tests for country tokenization on country index
* Adds countrynames-to-country.kb
* Adds country index and country field (in tabfill and with an upgrade script)
* Adds command line utility 'kbload', useful to load a new kb from file
* Automatically loads 'countrycode-to-country.kb' when installing demo site
* Ads configuration variable CFG_WEBSEARCH_INSTITUTION_COLLECTIONS