Expose "keep_regularized" argument for refit

[valpasq]

Need to expose keep_regularized argument for refit:

keep_regularized = TRUE
If lasso regression coefficient is fit to 0 in change detection stage, don't fit in refit stage.

keep_regularized = FALSE
Refit all coefficients in refit stage.

[ceholden]

What do you think about renaming it to something along the lines of stay_regularized instead? I wrote the keyword argument keep_regularized and it even confuses me sometimes as to what that means (i.e., "keep" meaning retain the regularized coefficients or do we keep with the regularization that happened?).

[valpasq]

Yes! I like stay_regularized much better since we want the coefficients that were regularized to stay regularized, as opposed to keeping the coefficients themselves.

[ceholden]

Implemented in commit referenced above.

refit_record function will retain keep_regularized kwarg for compatibility, but you can specify the behavior using stay_regularized in the config file. Just like the prefix, specify a list of True/False per refit method.