[SPARK-2788] [STREAMING] Add location filtering to Twitter streams

TwitterUtils.createStream(...) allows users to specify keywords that restrict the tweets that are returned. This change adds a location parameter that also restricts the returned tweets.
I'm having a bit of trouble here. I tried adding the following code to ensure binary compatibility, but it doesn't compile:
```scala
  def createStream(
      ssc: StreamingContext,
      twitterAuth: Option[Authorization],
      filters: Seq[String] = Nil,
      storageLevel: StorageLevel = StorageLevel.MEMORY_AND_DISK_SER_2
    ): ReceiverInputDStream[Status] = {
    createStream(ssc, twitterAuth, filters, Nil, storageLevel)
  }
```

When include that I get the following error:
```
[error] /home/shawn/Research/git-spark/spark/external/twitter/src/main/scala/org/apache/spark/streaming/twitter/TwitterUtils.scala:70: overloaded method value createStream with alternatives:
[error]   (jssc: org.apache.spark.streaming.api.java.JavaStreamingContext,twitterAuth: twitter4j.auth.Authorization)org.apache.spark.streaming.api.java.JavaReceiverInputDStream[twitter4j.Status] <and>
[error]   (jssc: org.apache.spark.streaming.api.java.JavaStreamingContext,filters: Array[String])org.apache.spark.streaming.api.java.JavaReceiverInputDStream[twitter4j.Status] <and>
[error]   (ssc: org.apache.spark.streaming.StreamingContext,twitterAuth: Option[twitter4j.auth.Authorization],filters: Seq[String],storageLevel: org.apache.spark.storage.StorageLevel)org.apache.spark.streaming.dstream.ReceiverInputDStream[twitter4j.Status] <and>
[error]   (ssc: org.apache.spark.streaming.StreamingContext,twitterAuth: Option[twitter4j.auth.Authorization],filters: Seq[String],locations: Seq[Seq[Double]],storageLevel: org.apache.spark.storage.StorageLevel)org.apache.spark.streaming.dstream.ReceiverInputDStream[twitter4j.Status]
[error]  cannot be applied to (org.apache.spark.streaming.StreamingContext, None.type)
[error]     createStream(jssc.ssc, None)
```
And similar errors for three more of the Java functions. @tdas Do you have any suggestions for how I can get this working?