This moves population and eviction of the "Persistence Cache" into WriteTransaction.

o Takes advantage of the fact that the exhaustive list of labels is known now, so replaces complex sorting/insert with simple replace.
o Does not address, but works around, the fact that labels are still longs in WriteTransaction. This needs to be addressed in a separate commit.
Ensure indexes are only reported as added if they actually have been created
Ensure constraint creation is idempotent from Cypher

o Change QueryContext.addIndexRule and createUniquenessConstraint to return IdempotentResult[V] instead of (V, Boolean)
Merge pull request #1343 from boggle/2.0-idempotency

2.0 idempotency
Fixes off-by-1 in BigLabelStoreGenerator
Merge pull request #1339 from jakewins/fix-cache-eviction

This moves population and eviction of the "Persistence Cache" into Write...