#58 Resolve "Registration form: Email validator does not trim"

Closes #58 (closed)

What does this MR do?

Trims the user-entered email address on the registration form so it validates and submits in the correct format.

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

Very confident

Links to related issues

None

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))