better str representation for HyperShuffleProducer
HyperShuffleProducer: more pythonic shortStr()

Just a little easier to read this way.
OrderBy: better shortStr

instead of columns[1,2], asc=[True, False], show [1+, 2-].
Merge pull request #256 from uwescience/shumo_better_hypercubeshuffle_tostr

Better str representation of HyperShuffleProducer