BibIndex: indexing only affected indexes
BibIndex: indexing only affected indexes

* Checks affected tags for every record, finds corresponding indexes
  and then reindexes only necessary indexes.  (closes #1573)

* Moves function add_recIDs_by_date outside WordTable
  to make WordTable API more clear/simple.

* Changes in bibindex_regression_tests, new interface for helper
  functions.

Signed-off-by: Grzegorz Szpura <900c4f131187ed2a7cfcf1f0200fa0b9c64b7780@cern.ch>
Tested-by: Tibor Simko <c7116e45300b163846dc01f3ed02116e3f8ef7a5@cern.ch>

inveniosoftware/invenio-search,tiborsimko/invenio-records,inveniosoftware/invenio-search,tiborsimko/invenio-search,inveniosoftware/invenio-records,tiborsimko/invenio-search,tiborsimko/invenio-records,inveniosoftware/invenio-records