Resolve "Start page / Front page content can be changed without devs"

Closes #470 (closed)

What does this MR do?

content of start page is set over cms

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

meh...

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))