Merge branch 'master' into driver

Conflicts:
	core/src/main/scala/spark/SparkContext.scala
	core/src/main/scala/spark/SparkEnv.scala
	core/src/main/scala/spark/deploy/LocalSparkCluster.scala
	core/src/main/scala/spark/executor/StandaloneExecutorBackend.scala
	core/src/main/scala/spark/scheduler/cluster/SparkDeploySchedulerBackend.scala
	core/src/main/scala/spark/scheduler/cluster/StandaloneClusterMessage.scala
	core/src/main/scala/spark/scheduler/cluster/StandaloneSchedulerBackend.scala
	core/src/main/scala/spark/storage/BlockManagerMaster.scala
	core/src/main/scala/spark/storage/ThreadingTest.scala
	core/src/test/scala/spark/MapOutputTrackerSuite.scala