Move annotation from one task to another

## Feature request

* The ability to move a single annotation from one task to another
* Earlier today I did a `task 23 start` to begin tracking some work I was doing. I had seen that 23 was the task I wanted from a previous run of `task list`. Unfortunately, a behind-the-scenes `task sync` had run and changed what task 23 was. Later, when I did `task 23 stop`, I realized the mistake. I needed to move the annotation of time start/stop from one task to another. (This would of course be useful if I'd simply added the wrong information to an annotation on a task)