Settings initializer

Notes:
- There are no default values besides the ones currently in the initializer file, so none of the settings can be removed.
- `strikes_for_ban` and `shelves` are not used in the application yet.
- The application must be restarted to change these settings.
- We might want to test changing the settings in our specs.
- There might be a nicer syntax for setting the variables in the initializer.