Fix typo in maxValue() - broke DL unpredictably.
Cosmetics.
Enable spirals test now that DL is working (after fixing b5aa268110)
Port over the FrameSplitter from h2o.
Port over JUnit test for DL missing values handling: Skip vs MeanImputation.
Add MissingValuesInserter to FrameUtils.
Merge branch 'master' of https://github.com/h2oai/h2o-dev