Add setters to BDate and BCalendarView

* BDate setters don't perform any validation, use with caution.
* BCalendarView setters do perform validation checks, and will adjust
the day so it fits the re

Add setters to BDate and BCalendarView

* BDate setters don't perform any validation, use with caution.
* BCalendarView setters do perform validation checks, and will adjust
the day so it fits the requested month or year.
* Add tests for the BCalendarView setters.

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