[SPARK-4382] Add locations parameter to Twitter Stream

When we request Tweet stream, geo-location is one of the most important parameters. In addition to the track parameter, the locations parameter is widely used to ask for the Tweets falling within the requested bounding boxes. This PR adds the locations parameter to existing APIs.
There is already a separate set of methods for Java, no? that use `Array` and not things like `Seq`. This is private to the Scala-based Spark code.