Move QueryRepresentation and Searcher supported query representation to QueryProvider- and Searcher- interfaces.
- UriParameters' fields are not allowed null.
- (WIP) Content negotiation for Zylab Patis Search client.
AIDA-33 #comment Fix: when iterating over query providers to retrieve all QueryIDs, step iterator only once per iteration.
AIDA-33 #comment fix: QName-constructor's parameter order is namespace uri, localpart, prefix.