Combined start and due date behavior

[johannesmono]

When setting start and due date to the same date without a time, the start date is deleted. A much more intuitive behavior to me would be (1) for the start date to be interpreted as 00:00 on this day and (2) for the due date as 23:59 on this day, as I want to start the todo on this day and have it done by the end of the day. Using times explicitely works as expected.