[Collideoscope] Whitespace tidy ups
[Collideoscope] Set the fallback body sender to Email

Because Collideoscope is based off the UK cobrand it falls back to
using the special Northern Ireland and London sending methods if
the DB doesn't specify one. We don't want that, but we do potentially
want to keep the devolved councils cleverness, so I've overriden
_fallback_body_sender only.

Fixes mysociety/FixMyStreet-Commercial#623
Pass cobrand into send_email_cron when sending SendReport emails

Without this, email sending within a cobrand will get the right main
email template (submit.txt) for the email - because it uses the
cobrand inside get_template - but it doesn't use the cobrand for
things like the email signature, because you have to pass it into
send_email_cron manually to make it cobrand-aware.

This probably hasn't been noticed before because most cobrands are
called Something FixMyStreet, but Collideoscope is different and hence
it caused a problem there.

Closes mysociety/FixMyStreet-Commercial#621.
Merge branch 'issues/621-collideoscope-email-signature' into smidsy