Impacted files:
* `basic_test.dart`: refactored
* `country_selector.dart`: refactored with a single `Column`
* `nutrition_page_loaded.dart`: refactored with a single `Column`
* `Podfile.lock`: wtf
* `product_list_user_dialog_helper.dart`: refactored with a single `Column`
* `product_refresh.dart`: replaced neutral with negative button
* `smooth_alert_dialog.dart`: removed the `advanced` constructor and the `neutral` button; simplified the display and made it work for `Column` bodies.
Deleted file:
* `product_list_dialog_helper.dart`
Impacted files:
* `basic_test.dart`: refactored
* `loading_dialog.dart`: refactored
* `product_dialog_helper.dart`: refactored
* `smooth_alert_dialog.dart`: now constructors for simple and advanced effects
* `user_contribution_view.dart`: now explicitly using the "advanced" dialog
* `user_preferences_profile.dart`: refactored
* `user_preferences_settings.dart`: now explicitly using the "advanced" dialog