[nag] Add Complete Task action to the task view

[Chuck Hagenbuch]

Quoting "Marcus I. Ryan" <marcus@riboflavin.net>:

> Okay...so this is kind of an example of my laziness, but I hate waiting
> to go into Modify task, setting it to complete and saving the changes,
> so in the task view, I added a Complete Task link (if the task isn't
> already completed).

Committed, thanks.

-chuck

--
Charles Hagenbuch, <chuck@horde.org>
"A dream which helps you to live your reality with dignity
 and justice is a good dream." - Tariq Ramadan