Added pluggable serializers and Kryo serialization

core/lib/kryo-1.04-mod/minlog-1.2.jar

core/lib/kryo-1.04-mod/reflectasm-1.01.jar

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

core/src/main/scala/spark/JavaSerializer.scala

core/src/main/scala/spark/KryoSerialization.scala

core/src/main/scala/spark/LocalFileShuffle.scala

core/src/main/scala/spark/Serializer.scala

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

run