Added partition aware union to improve reduceByKeyAndWindow
Added partitioner aware union, modified DStream.window.
Added flag in window operation to use partition awaare union.
Merge branch 'scheduler-update' into window-improvement

Conflicts:
	streaming/src/main/scala/org/apache/spark/streaming/dstream/WindowedDStream.scala
Added tests for PartitionerAwareUnionRDD in the CheckpointSuite. Refactored CheckpointSuite to make the tests simpler and more reliable. Added missing test for ZippedRDD.
Merge branch 'scheduler-update' into window-improvement
Fixed bug in PartitionAwareUnionRDD
Updated groupByKeyAndWindow to be computed incrementally, and added mapSideCombine to combineByKeyAndWindow.
Merge branch 'master' into window-improvement
Merge branch 'apache-master' into window-improvement
Removed unncessary options from WindowedDStream.
Added Apache boilerplate and class docs to PartitionerAwareUnionRDD.
Factor call site reporting out to SparkContext.
Make Python function/line appear in the UI.
Removed redundant TaskSetManager.error() function.

This function was leftover from a while ago, and now just
passes all calls through to the abort() function, so this
commit deletes it.
Merge pull request #311 from tmyklebu/master

SPARK-991: Report information gleaned from a Python stacktrace in the UI

Scala:

- Added setCallSite/clearCallSite to SparkContext and JavaSparkContext.
  These functions mutate a LocalProperty called "externalCallSite."
- Add a wrapper, getCallSite, that checks for an externalCallSite and, if
  none is found, calls the usual Utils.formatSparkCallSite.
- Change everything that calls Utils.formatSparkCallSite to call
  getCallSite instead. Except getCallSite.
- Add wrappers to setCallSite/clearCallSite wrappers to JavaSparkContext.

Python:

- Add a gruesome hack to rdd.py that inspects the traceback and guesses
  what you want to see in the UI.
- Add a RAII wrapper around said gruesome hack that calls
  setCallSite/clearCallSite as appropriate.
- Wire said RAII wrapper up around three calls into the Scala code.
  I'm not sure that I hit all the spots with the RAII wrapper. I'm also
  not sure that my gruesome hack does exactly what we want.

One could also approach this change by refactoring
runJob/submitJob/runApproximateJob to take a call site, then threading
that parameter through everything that needs to know it.

One might object to the pointless-looking wrappers in JavaSparkContext.
Unfortunately, I can't directly access the SparkContext from
Python---or, if I can, I don't know how---so I need to wrap everything
that matters in JavaSparkContext.

Conflicts:
	core/src/main/scala/org/apache/spark/api/java/JavaSparkContext.scala
Merge pull request #319 from kayousterhout/remove_error_method

Removed redundant TaskSetManager.error() function.

This function was leftover from a while ago, and now just
passes all calls through to the abort() function, so this
commit deletes it.
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/incubator-spark
Merge pull request #297 from tdas/window-improvement

Improvements to DStream window ops and refactoring of Spark's CheckpointSuite

- Added a new RDD - PartitionerAwareUnionRDD. Using this RDD, one can take multiple RDDs partitioned by the same partitioner and unify them into a single RDD while preserving the partitioner. So m RDDs with p partitions each will be unified to a single RDD with p partitions and the same partitioner. The preferred location for each partition of the unified RDD will be the most common preferred location of the corresponding partitions of the parent RDDs. For example, location of partition 0 of the unified RDD will be where most of partition 0 of the parent RDDs are located.
- Improved the performance of DStream's reduceByKeyAndWindow and groupByKeyAndWindow. Both these operations work by doing per-batch reduceByKey/groupByKey and then using PartitionerAwareUnionRDD to union the RDDs across the window. This eliminates a shuffle related to the window operation, which can reduce batch processing time by 30-40% for simple workloads.
- Fixed bugs and simplified Spark's CheckpointSuite. Some of the tests were incorrect and unreliable. Added missing tests for ZippedRDD. I can go into greater detail if necessary.
- Added mapSideCombine option to combineByKeyAndWindow.