Further dataframe batch consolidation.
Further dataframe batch consolidation.

* Concatinate small dataframe before shuffle.
* Omit shuffling of empty partitions.
    - This requires some adjustment to use the proxy object
      if *all* partitions from all workers are empty.

Projections, filterings, and aggregations are common operations
that often greatly reduce the size of a dataframe, and can result
in small output batches which have high relative overhead.

chamikaramj/beam,chamikaramj/beam,lukecwik/incubator-beam,robertwb/incubator-beam,robertwb/incubator-beam,apache/beam,robertwb/incubator-beam,lukecwik/incubator-beam,chamikaramj/beam,chamikaramj/beam,robertwb/incubator-beam,apache/beam,lukecwik/incubator-beam,lukecwik/incubator-beam,apache/beam,chamikaramj/beam,robertwb/incubator-beam,chamikaramj/beam,robertwb/incubator-beam,lukecwik/incubator-beam,apache/beam,chamikaramj/beam,lukecwik/incubator-beam,robertwb/incubator-beam,lukecwik/incubator-beam,robertwb/incubator-beam,apache/beam,lukecwik/incubator-beam,apache/beam,apache/beam,chamikaramj/beam,robertwb/incubator-beam,lukecwik/incubator-beam,apache/beam,chamikaramj/beam,apache/beam,robertwb/incubator-beam,lukecwik/incubator-beam,chamikaramj/beam,apache/beam,apache/beam