Allow @ function in edit task dialog

I really like the ability to add a role using the @ function with autofill.

However from the edit task dialog main line the @ function does not work. Autofill does not work and when closing the task dialog it does not add the role. The ~ function and ! function does work though.

Of course a role can be selected using the drop down menu, but I feel that for the sake of interface consistency the @ function should also work for the edit dialog, just as ~ and ! do.

Also, shortcuts like '@', '~', '!', and '...', really speed up Weekplan, perhaps they should have their own FAQ article? If there are more, I'd like to know them!

Thanks!