Major changes in 45.beta:
* Redesign the Month view to scroll infinitely to the future
  and past. It also displays events from other months, and
  allows creating events that span multiple months. Overall,
  it's pretty nice. I think I'm happy about it.
* Use modern widgets in the event editor dialog
* Use modern widgets in the calendar management dialog
* Use modern widgets in the event editor dialog
* Improve search performance and increase the range
* Various improvements to the event preview popover
* Add a menu shortcut for the Date & Time panel
* Port various message dialogs to AdwMessageDialog
* Add various shortcuts to common actions
* Load cached events immediately on startup
* Updated translations