Refactor foodsharepoint translations

Closes #906 (closed) and closes #545 (closed)

What does this MR do?

Break stuff, probably lots of translation refactoring, some minor refactoring in the area, you know the drill.

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

not very, to be honest. It's quite likely that I missed something here while untangling the spaghetti plate.

Links to related issues

• &7 (closed)
• #545 (closed)
• #890 (closed)
• #906 (closed)
• !1479 (merged)
• !1535 (closed)

How to test

Closely review the code changes in this MR, I guess?

Do lots of foodsharepoint-related stuff and look for translation problems.

Oh, and check the two commits that slightly adjust how the legal pages are presented.

Checklist

• adjusted the tests
• 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