BibRecord: filter field instances

* Introduces new function for filtering field instances obtained
  from record.  Function returns only those field instances that
  match some-other-subfield/some-other-value criteria.  The function
  can work in 'exact', 'substring' and 'regex' mode.
  (addresses #1550)

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

* Function record_get_field_values() now has additional
  parameters: filter_subfield_code, filter_subfield_value,
  filter_subfield_mode which allow to obtain only those
  field values that match certain filtering criteria.
  (closes #1550)

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

* Adds a warning when moving fails due to duplicates
  in target basket.

* 'move item' now works if a new basket is created
  during the move.

Signed-off-by: Krzysztof Lis <krzysztof.lis@cern.ch>
Tested-by: Tibor Simko <tibor.simko@cern.ch>
Merge branch 'master' into next

* master:
  WebBasket: 'move item' improvements
  BibRecord: record_get_field_values with filtering
  BibRecord: filter field instances

Conflicts:
	modules/bibrecord/lib/bibrecord_unit_tests.py

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>