Added HTML Email Formatting to Event Registration System

I added the capacity for administrators of my event registration system to send HTML-formatted confirmation emails, in addition to the originally offered plain-text confirmation emails. The system now provides a WYSIWYG interface with advanced formatting options to compose the message. For each (automated) message sent by the system, it sends the HTML version, as well as a dynamically generated text-only version for those with text-based email clients (e.g., some Blackberries).