fix(linky): encode double quotes when serializing email addresses

Email addresses can (under certain restrictions) include double quote
characters. See http://tools.ietf.org/html/rfc3696#section-3.

For example, `"Jo Bloggs"@abc.com` is a valid email address.

When serializing emails to the `href` attribute of an anchor element,
we must HTML encode these double quote characters. See
http://www.w3.org/TR/html-markup/syntax.html#syntax-attr-double-quoted

This commit does not attempt to improve the functionality (i.e. regex)
that attempts to identify email addresses in a general string.

Closes #8945
Closes #8964
Closes #5946
Closes #10090
Closes #9256