Update NEWS and CHANGES
[maven-release-plugin] prepare release 0.88
[maven-release-plugin] prepare for next development iteration
Add BoundedExecutor and ExecutorServiceAdapter
Add null check to ThreadPoolExecutorMBean
Update dense hll spec to reflect latest code
Update dense hll diagram
Allow specification of the time unit of TimeStat

TimeStat allows the time unit to be specified when adding a sample to the
distribution but when queried returns data implicitely converted to seconds.
This diff allows the time unit to be specified when a TimeStat is created
causing the returned data to be converted to the given unit.
Fix typo
Formatting