Add PairRDDFunctions.keys and values.
Add RDD.collect(PartialFunction).
Merge pull request #352 from stephenh/collect

Add RDD.collect(PartialFunction).
Fix typo.
Fix Accumulators in Java, and add a test for them
Add methods called just 'accumulator' for int/double in Java API
Merge pull request #351 from stephenh/values

Add PairRDDFunctions.keys and values.