Move REPL classes to separate module.

core/src/main/scala/spark/ClosureCleaner.scala

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

project/build/SparkProject.scala

repl/lib/jline.jar

repl/src/main/scala/spark/repl/ExecutorClassLoader.scala

repl/src/main/scala/spark/repl/Main.scala

repl/src/main/scala/spark/repl/SparkCompletion.scala

repl/src/main/scala/spark/repl/SparkCompletionOutput.scala

repl/src/main/scala/spark/repl/SparkInteractiveReader.scala

repl/src/main/scala/spark/repl/SparkInterpreter.scala

repl/src/main/scala/spark/repl/SparkInterpreterLoop.scala

.../src/main/scala/spark/repl/SparkInterpreterSettings.scala

repl/src/main/scala/spark/repl/SparkJLineReader.scala

repl/src/main/scala/spark/repl/SparkSimpleReader.scala

repl/src/test/scala/spark/repl/ReplSuite.scala