Refactored streaming project to separate out the twitter functionality.
Refactored kafka, flume, zeromq, mqtt as separate external projects, with their own self-contained scala API, java API, scala unit tests and java unit tests. Updated examples to use the external projects.
Added pom.xml for external projects and removed unnecessary dependencies and repositoris from other poms and sbt.
Removed unnecessary comments.
Removed extra empty lines.
Merge branch 'apache-master' into project-refactor
Added Scala and Python examples for mllib
Commented the last part of collaborative filtering examples that lead to errors
Added table of contents and minor fixes
Get rid of `Either[ActorRef, ActorSelection]'

Although we can send messages via an ActorSelection, it would be better to identify the actor and obtain an ActorRef first, so that we can get informed earlier if the remote actor doesn't exist, and get rid of the annoying Either wrapper.
Fixed several compilation errors in test suites
Fixed test suite compilation errors
Changed JavaStreamingContextWith*** to ***Function in streaming.api.java.*** package. Also fixed packages of Flume and MQTT tests.
Merge remote-tracking branch 'apache/master' into project-refactor

Conflicts:
	examples/src/main/java/org/apache/spark/streaming/examples/JavaFlumeEventCount.java
	streaming/src/main/scala/org/apache/spark/streaming/StreamingContext.scala
	streaming/src/main/scala/org/apache/spark/streaming/api/java/JavaStreamingContext.scala
	streaming/src/test/java/org/apache/spark/streaming/JavaAPISuite.java
	streaming/src/test/scala/org/apache/spark/streaming/InputStreamsSuite.scala
	streaming/src/test/scala/org/apache/spark/streaming/TestSuiteBase.scala
Added proper evaluation example for collaborative filtering and fixed typo
Minor typo fix for yarn client
Export --file for YarnClient mode to support sending extra files to worker on yarn cluster
Removed XYZFunctions and added XYZUtils as a common Scala and Java interface for creating XYZ streams.
Fixed examples/pom.xml and run-example based on Patrick's suggestions.
Fixed merge conflict