Database::get_ids_by_field_values() should process %opts fixing #32

Note that customer previously called:

    my $full_text_status = $session->get_repository->get_dataset( "eprint" )->get_field( "full_text_status" );
    my $filters = [ { fields=>[ $full_text_status ], value=>$opt }];
    my $vref = $field->get_ids_by_value( $session, $ds, filters=>$filters );

and they had to change this to:

    my $filters = [ { meta_fields=>[ "full_text_status" ], value=>$opt }];
    my $vref = $field->get_ids_by_value( $session, $ds, filters=>$filters );

in order for the fix to work.