Field selection as parameter

Allow the fields that are selected to be stored to be selected via a parameter. This will allow custom selection of which fields from the Google Maps results should be stored in the contact data.
We should maybe think about throwing an error or something if the field isn't found. That error will appear in the logs, and the user would see a message that looks something like `'An error occured, please try again later'`.

Not for this PR though.