Spark HTTP FileServer

Conflicts:
	core/src/main/scala/spark/SparkContext.scala

Log entire exception (including stack trace) in BlockManagerWorker.

logError API.

A general fileserver for both JARs and regular files.

Add shutdown hook to Executor Runner and execute code to shutdown local cluster in Scheduler Backend

Simulating a Spark standalone cluster locally

Add shutdown hook to Executor Runner and execute code to shutdown local cluster in Scheduler Backend

Log cache add/remove messages in block manager.

Added log messages on BlockManagerMaster to reflect block add/remove.
Also did some minor cleanup of storage package code.

Add a limit on the number of parallel fetches in the reduce stage

to the reduce function

one of the cluster schedulers.

issue with shared buffers in the KryoSerializer.

Disable running combiners on map tasks when mergeCombiners function is not specified by the user.