Add Java API

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

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

core/src/main/scala/spark/api/java/JavaDoubleRDD.scala

core/src/main/scala/spark/api/java/JavaPairRDD.scala

core/src/main/scala/spark/api/java/JavaRDD.scala

core/src/main/scala/spark/api/java/JavaRDDLike.scala

core/src/main/scala/spark/api/java/JavaSparkContext.scala

...ala/spark/api/java/JavaSparkContextVarargsWorkaround.java

.../scala/spark/api/java/function/DoubleFlatMapFunction.java

...rc/main/scala/spark/api/java/function/DoubleFunction.java

.../main/scala/spark/api/java/function/FlatMapFunction.scala

core/src/main/scala/spark/api/java/function/Function.java

core/src/main/scala/spark/api/java/function/Function2.java

...in/scala/spark/api/java/function/PairFlatMapFunction.java

.../src/main/scala/spark/api/java/function/PairFunction.java

...src/main/scala/spark/api/java/function/VoidFunction.scala

core/src/main/scala/spark/partial/PartialResult.scala

core/src/main/scala/spark/util/StatCounter.scala

core/src/test/scala/spark/JavaAPISuite.java

examples/src/main/java/spark/examples/JavaLR.java