The code added make the dialog show up. Probably anything else works,
but it's start to keep the project building while GcalManager migration
is finished and new GcalEditDialog is built.
Hooked signals from date and time entries.
Added comparison and adjustment if the interval.
Removed SimpleDate and SimpleTime structs.
Added _get_end_date for end-date change notification.
Added very initial support to handle obtention of the modified properties
of the edited event. There's still some kind of Model implementation to keep
track of the changes made by the user.
Georges Basile Stavracas Neto