When copying issues in different weeks, defaulting the date to today is unexpected

When copying issues in the calendar view, the date defaults to today. When looking at older weeks, this often causes the newly-created issue to vanish, as it will move to the current week.

In conjunction with #211, this makes it very easy to fail to correct the date and then the new issue vanishes into a different week.

I suggest that when copying an issue, the date defaults to the date of the copied issue. Then, there could be a quick, explicit, way to move the issue to "today" (for example a button next to the date input, and/or menu entry). Or, a configuration to default copied issues to "today" if that's an important and intentional workflow feature for some users.