Test Trig and RDF/JSON to test out the Rio Parser integration
add other Rio formats to verify nothing special about the given formats
parser.getName is ambiguous for RioParserImpl, use .toString instead
change PriorityCollection to use a ConcurrentSkipListSet internally

There are no alternatives to PriorityCollection for standard use of the
API, so it must be threadsafe.
make rio parsers not fail on datatype and language tag verification
make some more tests pass in maven by running them in separate threads
warnings removed, issue with PriorityCollection mitigated
more misbehaving comparators. Wrapped the sorting in a method to reuse
it