Remove unused index stats for MemoryTable
fixed bug in Export set, fifth argument now correctly determines the number of bits returned
Concurrent insert+statistics test
indexIterator gets another boolean for snapshot
TableStatus#getApproximateRowCount gets Session paramter.

Use getApproximate when computing statistics.

Use snapshot read for FDB getApproximate.
Use snapshot range scan for index statistics traversal
Updated behaviour for negative values of the fifth input argurment, similar to mysql
merge SytzeH: Bug fix in MExportSet

Merge pull request #1263 from SytzeH/sql-layer/expSet
https://github.com/FoundationDB/sql-layer/pull/1263
Transaction required
merge nathanlws: Snapshot reads for statistics generation

Merge pull request #1264 from nathanlws/sql-layer/stats-are-snapshot
https://github.com/FoundationDB/sql-layer/pull/1264
Merge remote-tracking branch 'github/master' into
catch-fdb-exception-commit-periodic

Conflicts:
	src/main/java/com/foundationdb/server/FDBTableStatusCache.java
	src/main/java/com/foundationdb/server/store/format/FDBStorageDescription.java