Add bookkeeping module.
Replace operations with respective vlf-tune wrappers.
Add basic tune strategies.
Save times instead of speeds,  compare on cumulative speed when tuning.
Add vlf-batch-size tuning in vlf-occur.
Move back to using average speed when measuring and tuning.  Be more
precise when choosing index for measurement.
Don't measure encoding of too small region when adjusting chunk start
and fix passing of elements to tune in vlf-occur.
Fix access to uninitialized measurements when tuning.
Add linear search for tuning and prefer smaller batches.
Apply batch size tuning on adjacent moves, search, save adjusting and
report total times.
Fix binary tune base case and add approximation after access to
previously queried measure that is still missing.
Fix write measuring and endless loop in nearby approximation.
Fix measure approximation and allow tuning to just over half file
batch.
Rename vlf-tune-optimal to vlf-tune-batch.
Change handling of measurement values to support approximations.
Tune batch size in more cases.
Restore batch size after save with adjustment.
Add function to linearly search best batch size according to existing
measurements and offer it when interactively changing batch size.
Apply and restore batch size in more cases.
Restore batch size and hexl mode in case of failed search or occur.