RP branded emails.

* Create a new model on the front end, rp_info.js, to keep things sane.
* Add new backend validation types: color and image
* Add backend tests to check backgroundColor and siteLogo
* Update the copy in HTML and text emails as per @ryanfeeley's suggestions.
* Loads of email styling updates to work across webmail and mobile.
* Use a common _header.html.ejs and _footer.html.ejs shared across all emails so updates are simpler
* Simplify the email template configuration - only specify the template filename, not the full path.
Boost the max POST body to 128kb to allow data URIs when staging an email address.
Pass the siteLogo whenever calling sendConfirmationEmail for unverified emails.