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 <grzegorz.szpura@cern.ch>
Tested-by: Tibor Simko <tibor.simko@cern.ch>
BibIndex: virtual global index

* Turns global index into a virtual index and
   hanges indexing engine to index virtual indexes
  during indexing physical indexes.  (closes #1574)

* Creates new idxINDEX_idxINDEX table which stores
  information about virtual indexes and their
  dependencies.

* Modifies functions for searching for affected
  indexes to be aware of virtual indexes.

* Adds miscellaneous index and field.

* Adds new tags for miscellaneous index.

* Enhances bibindex administration interface
  accordingly.

Signed-off-by: Grzegorz Szpura <grzegorz.szpura@cern.ch>
Tested-by: Tibor Simko <tibor.simko@cern.ch>
BibIndex: index type in admin interface

* Introduces administration interface
  for type of indexer: 'native', 'SOLR'
  'XAPIAN'.  Connects it with 'virtual'
  indexing.

Signed-off-by: Grzegorz Szpura <grzegorz.szpura@cern.ch>
Tested-by: Tibor Simko <tibor.simko@cern.ch>