Cross validation failing

[kyao]

Cross validation failing because Metric.get_function() method has been removed.

https://github.com/usc-isi-i2/dsbox-ta2/blob/master/python/dsbox/template/runtime.py#L470

The new way to call metric score is metricDesc.get_class()(**metric_description['params']).score(testY, ypred) , but testY and ypred now have to be D3M dataframe with d3mIndex column and the appropriate column metadadata.