WebSearch: CERN-specific collection sorting

* Sorts 'CERN Courier Issues/Articles' and 'CERN Bulletin
  Issues/Articles' collections by 773__y field in WebColl.
  (closes #2017)

Signed-off-by: Sebastian Witowski <sebastian.witowski@cern.ch>
Reviewed-by: Tibor Simko <tibor.simko@cern.ch>
Websearch: include 'cc' in RSS <channel>'s <link>

* If the 'cc' collection is defined when producing the RSS feed then
  it's included in the <link> tag under the <channel> tag.
  (closes #2013) (closes #2014)

Signed-off-by: Nikolaos Kasioumis <nikolaos.kasioumis@cern.ch>
Reviewed-by: Tibor Simko <tibor.simko@cern.ch>
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>
inveniocfg: affiliations in atlantis

* Computes affiliations during inveniocfg --load-demo-records
pep8 fix