Switched to using CompletionService, again.
Restored and Revised Previous ParallelMergeSort from earlier deletion.
Limited Merge Sort to upper portions of recursion.
Added Max_Depth to be used for larger ArrayLists to use another type of sort. (IE Question #5 on project 1).
Added Fallback to Exception Error to run the MergeSort in series rather than parallel if an error occurs.
Reverted Sort back to List using <T>.
Added Comparator to implement compareTo() during merge.
Added Additional Debug Information in Main().