Minor updates

- Changed settings of Google API
- City data can be edited in the frontend, if the user is a "superuser"
- Improved organisation of Impact Factors in categories and the
possibility to delete/connect Impact Factors dynamically to Best
Practices
- Improved error-pages
- Improved usability, for example by adding extra "Save"-buttons,
altering checkbox-widgets and sorting information in dropdowns
- Small bug-fixes