Provide docs to describe running on CDH/HDP cluster.

Adding Apache license to two files

0.8 Doc changes for make-distribution.sh

Fixed the bug that ResultTask was not properly deserializing outputId.

YARN build fixes

Docs describing Spark monitoring and instrumentation

This doc consolidates information relevant to CDH/HDP users in a single place.

SPARK-821: Don't cache results when action run locally on driver

[SPARK-864]DAGScheduler Exception if we delete Worker and StandaloneExecutorBackend then add Worker

Caching the results of local actions (e.g., rdd.first()) causes the driver to
store entire partitions in its own memory, which may be highly constrained.
This patch simply makes the CacheManager avoid caching the result of all locally-run computations.

SPARK-884: Add unit test to validate Spark JSON output

Updating assembly README to reflect recent changes in the build.

This unit test simply validates that the outputs of
the JsonProtocol methods are syntactically valid JSON.

Link the Spark UI up to the Yarn UI 

Return the port the WebUI is bound to (useful if port 0 was used)

Conflicts:
	core/src/main/scala/org/apache/spark/ui/UIUtils.scala
	core/src/main/scala/org/apache/spark/ui/jobs/PoolTable.scala
	core/src/main/scala/org/apache/spark/ui/jobs/StageTable.scala
	docs/running-on-yarn.md

Conflicts:
	core/src/main/scala/org/apache/spark/deploy/master/Master.scala