Default sort stores by added date (before it was by name)

What does this MR do?

The Stores-list https://beta.foodsharing.de/?page=betrieb&bid=1 gets default sorted by the added-on date descending.

How confident are you it won't break things if deployed?

very confident

Links to related issues

Checklist

• 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))
• Once your MR has been merged, you are responsible to update the #foodsharing-beta Slack channel about what has been changed here. They will test your work in different browsers, roles or other settings