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>