Range bookings system

[mjtamlyn]

• Add react to the site
• Basic bookings (Range scheduling #25)
• Cancellations (Range bookings v1.1 #26)
• Superuser cancellations (and more careful permission checking of cancellations in general)
• Improved error flows and testing
• Add missing uniqueness condition and fix the db duplicates, and prevent duplicate bookings for same archer at same time
• Convert records from range booking to an "Event"
• Book training group attendance in automatically
• Edit my booking to change distance, duration and target number
• Slack updates on bookings, edits and cancellations
• Duplicate booking template to following week (Create next booking template #31)
• First class modals (Modal improvements for range booking #32)
• See my upcoming bookings