Merge pull request #644 from shimingfei/joblogger

core/src/main/scala/spark/BlockStoreShuffleFetcher.scala

core/src/main/scala/spark/RDD.scala

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

core/src/main/scala/spark/Utils.scala

core/src/main/scala/spark/executor/Executor.scala

core/src/main/scala/spark/executor/TaskMetrics.scala

core/src/main/scala/spark/scheduler/DAGScheduler.scala

core/src/main/scala/spark/scheduler/JobLogger.scala

core/src/main/scala/spark/scheduler/SparkListener.scala

core/src/test/scala/spark/scheduler/JobLoggerSuite.scala

core/src/test/scala/spark/scheduler/SparkListenerSuite.scala