Add iCal Download Link for Event to Info, Thank-you pages and to Confirmation Email

This will allow folks who use iCal enabled calendars to quickly add the event to their calendar.

1. Modify the current iCal download function to support passing in an event ID.

2. Add a link to the iCal download for this event to the bottom of the Event/Page/EventInfo.tpl and Event/Register/ThankYou.tpl

• Link text = "» Add this event to your Outlook/iCal/Google Calendar" (put in <div class="action-link"> as usual)

3. Add this same link to ReceiptMessage.tpl - put it as the last line in the "Event Information and Location" section of the email.