BibIndex: indexing non-MARC standards
* Introduces NonMarcTermCollector for acquiring data
  from non-MARC records.

* Adds new column to tag table and inserts
  corresponding RecJson fields as another
  non-MARC value for 'tag'.

* Enhances test suite acordingly.

Signed-off-by: Grzegorz Szpura <grzegorz.szpura@cern.ch>
BibIndex: recjson fields in admin interface

* Admin interface shows recjson fields
  in logical fields overview.

* Fields and tags are shown directly in index
  overview.

* Edition of tag enhanced with option to
  change value for recjson field.

Signed-off-by: Grzegorz Szpura <grzegorz.szpura@cern.ch>