[MLLIB] SPARK-2329 Add multi-label evaluation metrics

Implementation of various multi-label classification measures, including: Hamming-loss, strict and default Accuracy, macro-averaged Precision, Recall and F1-measure based on documents and labels, micro-averaged measures: https://issues.apache.org/jira/browse/SPARK-2329

Multi-class measures are currently in the following pull request: https://github.com/apache/spark/pull/1155
Ah, `sum` is defined in `DoubleRDDFunctions`. But looking at the `map` call, it seems like it would produce an `RDD[Double]`? I would think you can call `sum`, if you import `org.apache.spark.rdd.DoubleFunctions` maybe? Up to you what you like better.