- Added a StorageLevels class for easy access to StorageLevel constants
  in Java
- Added doc comments on Function classes in Java
- Updated Accumulator and HadoopWriter docs slightly

- Add override keywords.
- Cache RDDs and counts in TC example.
- Clean up JavaRDDLike's abstract methods.

- Replace JavaLR example with JavaHdfsLR example.
- Use anonymous classes in JavaWordCount; add options.
- Remove @Override annotations.

Add distinct() method to RDD.

Fix bug in DoubleRDDFunctions.

(you can no longer iterate over a Source multiple times).

LocalKMeans runs locally with a randomly generated dataset.
SparkLocalKMeans takes an input file and runs KMeans on it.

When a task throws an exception, the Spark executor previously just
logged it to a local file on the slave and exited. This commit causes
Spark to also report the exception back to the driver using a Mesos
status update, so the user doesn't have to look through a log file on
the slave.

Here's what the reporting currently looks like:

    # ./run spark.examples.ExceptionHandlingTest master@203.0.113.1:5050
    [...]
    11/10/26 21:04:13 INFO spark.SimpleJob: Lost TID 1 (task 0:1)
    11/10/26 21:04:13 INFO spark.SimpleJob: Loss was due to java.lang.Exception: Testing exception handling
    [...]
    11/10/26 21:04:16 INFO spark.SparkContext: Job finished in 5.988547328 s

Note that we use scala.Serializable introduced in Scala 2.9 instead of
java.io.Serializable. Also, case classes inherit from scala.Serializable by
default.

tabulate used if indexed used by function and fill otherwise.