Food expiry remainder

Dec 9, 2018

- Reminders with setting the number of days before the expiration date
- Export all foods to file
- Export some foods to a file
- Export foods database to file
- Export of some foods from the database to a file
- Import foods from a file (add, replace or remove previous foods)
- Import of foods database from file (add, replace or delete previous ones)
- Fixed some bugs