[streaming] DataStream output naming reworked from vertex to edge based model
[streaming] Iterative DataStreams updated with buffer timout and max wait time
[streaming] DataStream fix to return DataStreamSink on closing operators
[streaming] GroupReduce operator added + StreamCollector bugfix
[streaming] Implemented sliding window and batchReduce
[streaming] Added groupBy operator to DataStream + name refactor
[streaming] Updated operator test to avoid environment execution
[streaming] Several minor bugfixes
Merge remote-tracking branch 'upstream/streaming-ready' into iterative