Email address change verification email should contain new email address

[slaFFik]

When user changes his email on this page: /members/slaffik/settings/ - in the verification email he should see the new email address, he is changing to.

Good for preventing hacks, wrong changes etc.

[slaFFik]

Initially found by @oksankaa. She didn't have an account, so I created issues on her behalf.

[djpaul]

In 10717:

Emails: in the settings-verify-email-change email, include the user/recipient's email address in the body text.

This will help explain to users what's been happening and hopefully help keep people aware of accidental changes or hack attempts.
Emails will have to be reinstalled via the repair tool for sites to see this change.

Fixes #7034

Props oksankaa

[DJPaul]

Thanks very much for reporting these problems, @oksankaa!

[DJPaul]

Note: we'll need to try to include a line somewhere on the 2.6 release notes/welcome screen explaining that if people want this improvement on their site, that they'll need to go into the repair tools and reinstall the emails.