Documentation Needed for Gmail with Two-Step Verification

[wmbeers]

This is purely a documentation issue, but if you are using Gmail's SMTP server and have two-step verification enabled, you have to create an app-specific password and use that in the config.

The page for setting up app-specific passwords is https://security.google.com/settings/security/apppasswords

Adding a note to this effect in the comments added to web.config would be helpful.