V1.2.0 improvements

A few improvements to be included in the 1.2.0 release.  Most of this commit is focused around performance improvements in the TaskExecutorDistributor and the TaskSchedulerDistributor.

Other improvements included in this merge:
* Added deprecation notices for things that will be removed in 2.0.0
* Fixed not handling low priority task delays correctly in the statistic tracker implementation
* General cleanup in javadocs and code