Cleans up users adderssfield country

- Provides addressfield option to override address country with affiliate country
- Adds the option to chain of users address filters
- Changes registration form: replaces hardcoded country with affiliate country
- UK and Canada registration: removes hardcoded country in favor of common solution
- UK and Canada user creation on login: replaces hardcoded country with affiliate country
Merge pull request #3396 from sergii-tkachenko/cleanup-affiliate-country

Cleans up users adderssfield country