Fix typo
Fix date format when cloning/editing a booking
Properly send registrant email to organizer

Even if all emails to the registrant are disabled, the organizer should
still be able to get an email notification.
PEP8
Use correct time(zone) in alarm emails
Fixed wording of notification
Fix abstract fields not showing up in the book

* Also, show and hide them according to the settings
Fix event arrival dates when start_time > end_time
Timetable arrows shifted when less than 20 mins
Code simplification and visual improvements
Wording - 'Edition' -> 'Edit'
Nicer HTML color -> RGB conversion function

Properly handles 3-digit hex codes too.
PEP8/style fixes