Updated JavaStreamingContext to make scaladoc compile.

`sbt/sbt doc` used to fail. This fixed it.
Merge branch 'scaladoc1' of github.com:rxin/incubator-spark into graphx
Miscel doc update.
Merge branch 'graphx' of github.com:ankurdave/incubator-spark into graphx

Conflicts:
	graphx/src/main/scala/org/apache/spark/graphx/Pregel.scala