Fix updating objects with password fields

Calling set_data in prepare_update led to double hashed passwords on
update because it was called once in update_data and right after that
again in prepare_update. Remove prepare_update and instead use set_data
for inserts as well.
Implement password repeat check in JavaScript
Fix a warning during test runs
Add a date picker for custom/reservation/reserve
Implement Attribute::Time
Start and end time for reservations
redirect after post for Custom::Reservation::reserve
Add import.sh to .gitignore
Port Date and Image attribute tests to new testing infrastructure
Implement Attribute::Time::format
Implement Attribute::Date::is_today
Show today's date as 'Heute' in reservation list
Allow combining CiderCMS dispatch type with Args
Implement cancellation of reservations
Allow filtering string attributes for undef
Only mark cancelled reservations as such, don't delete them
More structure for default login form