Adds CleanupService for auto-closing ResourceIterators on GC.

o Adds AutoCleanupResourceIterator to be used by the core API
o IndexNotOnlineException caus we gonna need it next
o Neo4jJobScheduler now uses daemon threads
Hooks in CleanupService for all ResourceIterators

o Ensures that IAGD dependency resolver only performs correct casts
o Javadocs for ResourceIter*
o Makes Node.getLabels return a ResourceIterable
o Makes IndexHits ResourceIter*
Documents ResourceIterator.close() in the core API tutorial & related fixes

o Adds close() example to schema indexing tutorial
o Adds note on how to handle ResouceIter*
o Fix: Makes ROProxy use ResourceIter*
o Fix: Makes ha/lock/LockableNode use ResourceIter*
Merge pull request #671 from boggle/close-index-readers

Close index readers