Checkpoint.
Checkpoint.
Cleanups and adds performance regression.
checkpoint.
Checkpoint.
Conditionalize LevelDB index retrievals.

The LevelDB index retrievals could be repeated in a given operation
batch if multiple queued mutations affect the same (Label Name) singles
and (Label Name, Label Value) doubles.  This is wasteful and
inefficient, as a single retrieval suffices.  Thusly this commit
retrieves the canonical index mappings if the said mapping has not
been looked up in a given batch.
Oops.
Address outstanding PR comments.
Encapsulate fingerprint frontier checks in renderView().
Make LevelDB chunk size a flag.
Set -leveldbFlushOnMutate to false by default.
Small cleanups and comments in tiered storage.
Fix tiered storage test to trigger iterator rewinding case.
Set test time to fixed value.
Add data extraction methods to operator types.
Add operator value extraction tests.
Comment out panicking test until proper support is implemented.
Minor tiered storage fixups.
Add tests for and fix getValuesAlongRangeOp value extraction.
Run ``make format``.