[SPARK-1210] Prevent ContextClassLoader of Actor from becoming ClassLoader of Executo...

...r.

Constructor of `org.apache.spark.executor.Executor` should not set context class loader of current thread, which is backend Actor's thread.

Run the following code in local-mode REPL.

```
scala> case class Foo(i: Int)
scala> val ret = sc.parallelize((1 to 100).map(Foo), 10).collect
```

This causes errors as follows:

```
ERROR actor.OneForOneStrategy: [L$line5.$read$$iwC$$iwC$$iwC$$iwC$Foo;
java.lang.ArrayStoreException: [L$line5.$read$$iwC$$iwC$$iwC$$iwC$Foo;
     at scala.runtime.ScalaRunTime$.array_update(ScalaRunTime.scala:88)
     at org.apache.spark.SparkContext$$anonfun$runJob$3.apply(SparkContext.scala:870)
     at org.apache.spark.SparkContext$$anonfun$runJob$3.apply(SparkContext.scala:870)
     at org.apache.spark.scheduler.JobWaiter.taskSucceeded(JobWaiter.scala:56)
     at org.apache.spark.scheduler.DAGScheduler.handleTaskCompletion(DAGScheduler.scala:859)
     at org.apache.spark.scheduler.DAGScheduler.processEvent(DAGScheduler.scala:616)
     at org.apache.spark.scheduler.DAGScheduler$$anonfun$start$1$$anon$2$$anonfun$receive$1.applyOrElse(DAGScheduler.scala:207)
     at akka.actor.ActorCell.receiveMessage(ActorCell.scala:498)
     at akka.actor.ActorCell.invoke(ActorCell.scala:456)
     at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:237)
     at akka.dispatch.Mailbox.run(Mailbox.scala:219)
     at akka.dispatch.ForkJoinExecutorConfigurator$AkkaForkJoinTask.exec(AbstractDispatcher.scala:386)
     at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
     at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
     at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
     at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)
```

This is because the class loaders to deserialize result `Foo` instances might be different from backend Actor's, and the Actor's class loader should be the same as Driver's.

Author: Takuya UESHIN <ueshin@happy-camper.st>

Closes #15 from ueshin/wip/wrongcontextclassloader and squashes the following commits:

d79e8c0 [Takuya UESHIN] Change a parent class loader of ExecutorURLClassLoader.
c6c09b6 [Takuya UESHIN] Add a test to collect objects of class defined in repl.
43e0feb [Takuya UESHIN] Prevent ContextClassLoader of Actor from becoming ClassLoader of Executor.
Make sed do -i '' on OSX

I don't have access to an OSX machine, so if someone could test this that would be great.

Author: Nick Lanham <nick@afternight.org>

Closes #258 from nicklan/osx-sed-fix and squashes the following commits:

a6f158f [Nick Lanham] Also make mktemp work on OSX
558fd6e [Nick Lanham] Make sed do -i '' on OSX
SPARK-1096, a space after comment start style checker.

Author: Prashant Sharma <prashant.s@imaginea.com>

Closes #124 from ScrapCodes/SPARK-1096/scalastyle-comment-check and squashes the following commits:

214135a [Prashant Sharma] Review feedback.
5eba88c [Prashant Sharma] Fixed style checks for ///+ comments.
e54b2f8 [Prashant Sharma] improved message, work around.
83e7144 [Prashant Sharma] removed dependency on scalastyle in plugin, since scalastyle sbt plugin already depends on the right version. Incase we update the plugin we will have to adjust our spark-style project to depend on right scalastyle version.
810a1d6 [Prashant Sharma] SPARK-1096, a space after comment style checker.
ba33193 [Prashant Sharma] scala style as a project
fail all jobs when DAGScheduler crashes for some reason
logging error reason
minimize the influence to the jobs
kill application when the exception was thrown
check if DAGScheduler is shutdown in SparkContext
style fix
add test case
make code more testable and fix test cases
style fix
further style fix
stop the eventActor from supervisor
fix
fix code indentation
style fix
create eventActor in the constructor of DAGScheduler