Fix bug: DoubleRDDFunctions.sampleStdev() computed non-sample stdev().

Update JavaDoubleRDD to add new methods and docs.

Fixes SPARK-825.
Merge pull request #722 from JoshRosen/spark-825

Fix bug: DoubleRDDFunctions.sampleStdev() computed non-sample stdev()
Fix a test that was using an outdated config setting
Add JavaAPICompletenessChecker.

This is used to find methods in the Scala API that
need to be ported to the Java API.  To use it:

  ./run spark.tools.JavaAPICompletenessChecker
Conflicts:
	project/SparkBuild.scala
	run
	run2.cmd
Remove annotation code that broke build.
Merge branch 'master' of github.com:mesos/spark