[Aleph rest-dlf connector & tests] Made AlephRequestItemService capable of requesting multiple items at once
Problem with only one possible itemId returned on output solved with joining all ids into one with special delimiter defined in AlephConstants as REQUEST_ID_DELIMITER = ";"
Also modified test AlephRequestAndCancelRequestTest so that it passes three items to request & afterwards it cancells them.
Also there will be no more ItemOptionalFields nor UserOptionalFields included in any of these services. Which means toolkit.properties was made better maintainable.