Small clean up
Add the configuration of the LDAP login attribute

 - makes the LDAP login attribute configurable (through the LDAP authentication system config in indico.conf)
 - the login attribute now defaults to 'uid' instead of 'cn' if not specified in the configuration
 - fixes #1593
Default to uid in the example config
Properly import Config
Cleanup imports
Fix blocking check; mark all CandBars as ConfBars
Consider flexibility when marking conflict bars
Improve single booking warning with only conflicts

Display a better message when during a simple booking, all the occurences are conflicting.
Also prevent from "confirming" this invalid booking and go to the next step.
Avoid querying in a loop in blocking list
Create alembic version table in public schema

For some reason it ends up in the indico schema in production
Add repetition info on booking creation email
Prevent sending reminders on booking creation
Add get_month_start/end helpers
Add round_up_month helper
Add Room.is_in_digest_window
Add weekly reservation digest

Add email template and scheduler task.
Disable sending reminder for weekly occurrences.
Mark weekly occurrences created within digest window as notified.
English: 'booking at' -> 'booking under'
Add global setting to disable reminders
Add migration revision
Add per-room setting to disable reminders