Add "One-Click Booking" ability

Added One-Click Booking. In the Admin form or on the Calendar edit form it's a checkbox. It will only work if you're using the default Calendar display, or should probably work if you are outputting the Opening Instances default display. If it's enabled, a user is logged in, and the template preprocess for Opening Instances is running it will attach some JS to allow One-Click booking.

This is pushed in latest 2.2.x

This is live in 2.2.3 → .