Add Pilot events to api.wordpress.org/events

[iandunn]

That'll be needed for them to show up in the Events Widget in Core.

• [x] #885
• [ ] Make any changes to the default CPT API endpoint needed, like registering extra fields
• [ ] Update official-wordpress-events to fetch pilot events from the new endpoind, and cache them in the wporg_events tables
• [ ] Eventually, we'll probably need some changes in Core to distinguish these from WordCamps, but for now we can probably just have some code in the api.w.org endpoint that sets the type to wordcamp

Longer term, and maybe outside the scope of this ticket:

• [ ] Maybe update Core to show a different icon etc for pilot events. Discuss w/ Community team first to see what they want.
• [ ] After we update Core, we can change the API to only set the type as wordcamp if the user agent is an older version of Core.

[iandunn]

Since we ended up using the wordcamp CPT, we may not need to do many of these changes. We should check once Rome or Tokyo are on the schedule, though.