fix size estimator statistics
style fix
JavaDoc
Merge pull request #2448 from ahmetmircik/fixSizeEstimatorStasts

Fix size estimator statistics
mark testRemoveObjectDelayDefault as problematic
add > 0 check
mark test as problematic
some tiny refactoring use existing record store, do not create a new one.
Overview, Map improvements.
Added first aggregation classes
Trying to get first aggregation running
Added emit to aggregation mapper
Added emit to aggregation mapper