Fix block manager UI display issue when enable spark.cleaner.ttl

[Spark-753] Fix ClusterSchedulSuite unit test failed 

Fixing bug in BlockManager timeout

Bump akka and blockmanager timeouts to 60 seconds

Unpersist More block manager cleanup.

BlockManagerMasterActor.

Implemented a removeRdd method in BlockManager, and use that to
implement RDD.unpersist. Previously, unpersist needs to send B akka
messages, where B = number of blocks. Now unpersist only needs to send W
akka messages, where W = the number of workers.

This prevents Spark from changing the original file's permission, and
also allow add file to work on non-posix operating systems.

Netty and shuffle  bug fixes

Conflicts:
	core/src/test/scala/spark/ShuffleSuite.scala

Skip fetching zero-sized blocks in NIO.

Also unify splitLocalRemoteBlocks for netty/nio and add a test case

Remove unused addIfNoPort.

Also convert the local-cluster test case to check for non-zero block sizes

Use default classloaders for akka & deserializing task results

a. Fix the port number by reading it from the bound channel
b. Fix the shutdown sequence to make sure we actually block on the channel
c. Fix the unit test to use two JVMs.

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.