Recast Aggregator to subsume AggregateReducer.
WIP: Moving towards the new organization for aggregators.
WIP: Restructuring in progress. Basic aggregator/tansfer realignment done.
WIP: Restructuring continues.  Can run serial-spatial.
WIP: Resturcturing continues.  Builds without errors; Rendering stategies all work.
WIP: Reformulating.  Passes automated tests and most demos.
Restructured version passes all tests.  AggregateReducers is removed.
Performance tuning some presets.