Use default classloaders for akka & deserializing task results

Fix CheckpointRDD java.io.FileNotFoundException when calling getPreferredLocations

Use ec2-metadata in start-slave.sh to detect if running on EC2

[SPARK-663]Implement Fair Scheduler in Spark Cluster Scheduler 

NonJavaSerializableClass should not be Java serializable...

serializable.

Automatically configure Netty port.

local-cluster pass. Previously they were failing because Netty was
trying to bind to the same port for all processes.

Pair programmed with @shivaram.

bug fix: Shuffle block iterator is ignoring the shuffle serializer setting.

block iterators for local blocks. Also added a unit test for that.

PR #419 applied the same change, but only to start-master.sh,
so some workers were still starting their web UI's using internal
addresses.

This should finally fix SPARK-613.

Exclude old versions of Netty from Maven-based build

Use ARRAY_SAMPLE_SIZE constant instead of hard-coded 100.0 in SizeEstimator

DistributedSuite: remove dead code

Throw exception if TaskResult exceeds Akka frame size

called.

Conflicts:
	core/src/main/scala/spark/SparkContext.scala
	core/src/main/scala/spark/scheduler/cluster/ClusterScheduler.scala
	core/src/main/scala/spark/scheduler/cluster/TaskSetManager.scala

Maven build fix & two other small changes

check for core classes in run. This fixed the problem that core tests
depend on whether repl module is compiled or not.

Manual merge & cleanup of Shane's Shuffle Performance Optimization