Swipe consistency between days/weeks/months

Originally part of Overview of tasks without due dates.

It takes a while to learn where you can and can't swipe to change the day/week/month/year. Currently swiping does nothing on Tasks, Notes, and Events created in Bullet — but DOES work on items from integrated calendars, which is confusing.

Proposed fix: make swipes on integrated-calendar items also do nothing, so the safe swipe targets are consistent (empty space, separators, or date headers).