Small features for improving Abby's experience

[Seth Nickell]

> > 
> > * Let Abby mark e-mail messages as tasks, and have due dates set on
> > them. E-mail is the most common place for people to store todo items.
> > Support this existing behavior better.
> 
> Evolution has half of this feature already.  If you rightclick on an
> email and select "Follow Up" you can enter a day (and time) by which the
> email needs to be followed up. 

Its very important not to require a due date, and to make marking as a
task very simple (I suspect we should just replace "important" with
"task", or perhaps just put all important messages in the task list).
Most tasks don't have due dates, per se, they are just reminders.

-Seth