[Zurich] email templates point to surveys

Fixes https://github.com/mysociety/FixMyStreet-Commercial/issues/464

Also requires mysociety-servers.git@45e3a5d3 for the /umfrage redirect.
Merge branch 'issues/commercial/464-zurich-email-templates-for-evaluation'
[Bromley] Reduce detail field character limit to 1750

"The length of 2000 characters is causing some issues in the underline
back office application."

Updated to include a comment making it (hopefully) clearer which council
this is for - thanks @davewhiteland!
Default lastname of '-' if none found.
Merge remote-tracking branch 'upstream/master'