Change default time for task execution

[gehinz]

User experience can be improved by setting 22:00 as the default for tasks that move a user out and 12:00 for tasks that move users to another dorm.

[lukasjuhrich]

Note to self:

• In here we will need to replace utc.time_min() by day before + tz-annotated 22:00

@gehinz In light of the fact that the time when moving can be set manually, do you still think it's necessary? Because changing the default time from night to day might be a bit unexpected.

[gehinz]

Changing the default for moving might be considered less important, but still would be nice (or prefill the Time input field with 10:00?). Changing the default for membership cancelations to something that is close to the end of the day is still needed as there's no reason to have individual time settings for cancellation. Just add +21h or +22 to the UTC Date.

[lukasjuhrich]

tl;dr: prefill the form field and don't make it optional again.