WIP: fix amount per slot
What does this MR do?
This MR fixes the issue #335 by dividing the amount of food saved through the number of used slots for each pickup.
How confident are you it won't break things if deployed?
- 80% on the technical side
- 30% on the user acceptance side
Links to related issues
- added a test, or explain why one is not needed/possible...
- no unrelated changes
- asked someone for a code review
- joined #foodsharing-beta channel at https://slackin.yunity.org
- added an entry to CHANGELOG.md (description, merge request link, username(s))