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
Rename Neo4jMockitoHelpers static utility methods to better express intent
Merge pull request #972 from boggle/2.0-primlongs

Make EntityReadOperations return PrimitiveLongIterator