[Events 2.0] Embed the contact's email address in the event invitation

Unlike Legacy Events, Events 2.0 lacks the contact's email address embedded in the event invitation "Register" (and decline) button hyperlink coding, i.e., http://events.r20.constantcontact.com/register/regform?oeidk=..., which in addition to identifying the event, also identifies the registrant by their (Constant Contact stored) email address, and automatically populates the "Email Address" field in the registration form. This not only speeds up the registration process (less inputting) but also aids in ensuring the registrant uses the CC-stored email address, and helps prevent placing multiple registrations for an event, if this Legacy Event function worked in Events 2.0 - see this thread.