Expose `col_types` parameter in CLI arguments.

[johngian]

This was really useful when I recently used automl_gs. It looks like you can override the column types if you are programmatically running automl_gs but not through CLI.

[minimaxir]

I left it out because I wasn't sure how to optimally pass a dict through the command line. This approach should work though.

[robotenique]

How exactly would one use the col_types dict? Suppose I have one feature named "feature1" with type str and my target is called "survival" and is an int. How should I write this col_types dict?

edit: this is more of something I was struggling before when using automl-gs in python itself :'0