Events: Add checkbox for Email Opt-In

When you have Events, you will be able to express information to your customers that they can opt-in or opt-out to receive emails from you based on them participating with this Event.

A Couple items to note:
-- if enabled, a pre-checked checkbox and default wording are added to Every event order form to capture user emails.  Event user must opt out (unselect the check mark). Here is an example of the default response you can provide to your customers

 "I agree to receive marketing emails from <client name> at the address provided."

-- Email is captured in the Excel sheet and can be exported and uploaded into whatever Contact mgmt tool they use. 

-- This feature is Rule Based. If enabled, would automatically show on all Events.