PipelineSweeperMacro incorrect column purpose inference #460

PipelineSweeperMacro tries to infer the Purpose of the columns in the data-set, and then generates the parameter space to sweep over.

For several datasets, it infers the purpose incorrectly e.g. for some datasets, the PipelineSweeperMacro ended up using the label column as a feature. There is currently no way for the user to override this behavior.

The proposal is to add arguments to the PipelineSweeperMacro, corresponding to the intended purpose for a particular column. Purpose inference will be done only on columns which were not specified by the user.