Do double conversion inside fitRegression

[mchav]

fitRegression doesn't work for arbitrary num types. It defaults to double. The current behaviour when a user passes in a dataframe with other num types is to filter all of them out. We can do an implicit conversion inside fitRegression.

[mchav]

You'd also need to add the conversion logic to the final model.

[ashwinmathi]

Started looking into this, could we just return the modified dataframe from the fit function along with the models or would that be smelly