TODO's behavior in agenda and month views


Here are the rules for how/when/where should to-dos be displayed in agenda/month view:

* startDt doesn't influence to-do behavior, it's irrelevant
* To-dos without dueDt aren't shown
* The time component doesn't influence the behavior in month view, only agenda
* Overdue to-dos appear today, and not at dtDue, so we don't forget them
* In agenda, if the to-do is overdue and has time, it should appear in the all
  day area  because, since it's overdue, you must do it ASAP and not wait for the
  original time.

* In agenda, a not-overdue to-do, with time, is drawn with the rectangle ending
  at dtDue, and not starting at dtDue. If dtDue is at 00h00, then it should be
  displayed in the previous day, ending at 23:59:59