Skip NodeRecords that are not in use when scanning the store during population

o Make NeoStoreIndexStoreView.NodeLabelFilterPredicate skip unused nodes
o Add basic store scan test for NeoStoreIndexStoreView
o Add TargetDirectory.cleanTestDirForTest
Merge pull request #818 from boggle/2.0-dont-index-removed-nodes

Skip NodeRecords that are not in use when scanning the store during popu...