mandatory transactions for server
o ensured tests create transactions as appropriate
o ensured RestfulGraphDatabase, BatchOperationsService and CypherService are wrapped in TransactionFilter
o ensured streaming output is written before TransactionFilter finishes transaction
Fixes docs bugs for new indexing in core API.
Make nodesGetForLabel return PrimitiveLongIterator

o Introduce helpers for mapping and filtering PrimitiveLongIterator
o Add DiffSets.applyPrimitiveLongIterator
Make nodesGetFromIndexLookup return PrimitiveLongIterator

o Introduce Neo4jMockitoHelpers.{asAnswer|asPrimitiveAnswer}
o Make IndexReader.lookup return PrimitiveLongIterator
o Introduce JavaConversionSupport for converting PrimitiveLongIterator to scala Iterators
o Delete unused PrimitiveIteratorUtil
o Replace use of HitsIterator with a PrimitiveLongIterator from Hits
Make nodeGetLabels return PrimitiveLongIterator