#11 To-do 'Cancelled' state

(as per requested by Peter)

Currently, when I don't complete a to-do, I delete that
particular to-do and archive it. This usually works,
but some times, displaying something as 'Cancelled'
would be very helpful, eg beaming to another Projects
user. Instead of a 'tick' in a circle, it would be a
cross, or even text with a strikethrough.

Cheers