Cancel uncompleted tasks when rolled over

When rolling a task over to the next day, it would be helpful to have the option change its status to cancelled on the day it's coming from. This will allow me to keep task reports tidy by excluding cancelled tasks from my queries.

e.g.

```md
- [ ] this is a task that is getting rolled over
```

to

```md
- [-] this is a task that is getting rolled over
```