Improvements

Hide category field in event creation dialog if there are no subcategories (#3112)
Remove length limit from registration form field captions (#3119)
Use semicolons instead of commas as separator when exporting list values (such as multi-select registration form fields) to CSV or Excel (#3060)
Use custom site title in page title (#3018)
Allow manually entering dates in datetime fields (#3136)
Send emails through a celery task. This ensures users do not get an error if the mail server is temporarily unavailable. Sending an email is also retried for a while in case of failure. In case of a persistent failure the email is dumped to the temp directory and can be re-sent manually using the new indico resend_email command (#3121)
Reject requests containing NUL bytes in the query string (#3142)

Bugfixes

Do not intercept HTTP exceptions containing a custom response. When raising such exceptions we do not want the default handling but rather send the custom response to the client.
Do not apply margin for empty root category sidebar (#3116, thanks @nop33)
Fix alignment of info-grid items on main conference page (#3126)
Properly align the label of the attachment folder title field
Fix some rare unicode errors during exception handling/logging
Clarify messages in session block rescheduling dialogs (#3080)
Fix event header bar in IE11 (#3135)
Fix footer on login page (#3132)
Use correct module name for abstract notification emails in the event log
Remove linebreaks from email subject in paper review notifications
Fix extra padding in the CFA roles dialog (#3129)
Do not show an extra day in timetable management if an event begins before a DST change
Disable caching when retrieving the list of unscheduled contributions
Process placeholders in the subject when emailing registrants
Fix Shibboleth login with non-ascii names (#3143)

Add new is_ticket_blocked signal that can be used by plugins to disable ticket downloads for a registration.