Use existing rest endpoints for baskets

What does this MR do?

Uses the already existing rest endpoints for deleting baskets and for listing the coordinates on the baskets map instead of ajax requests.

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

Very sure

How to test

1. Checkout branch locally
2. Login as foodsaver

Deleting a basket:

3. Open one of your active baskets from the topbar
4. Click "Essenskorb löschen"
5. You should see a confirmation message

List of basket coordinates:

3. Go to the baskets map http://localhost:18080/essenskoerbe/find
4. Check if you see map markers

Checklist

• added a test, or explain why one is not needed/possible... unit tests for the endpoints already exist
• 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