Make it possible to delete an entire statement

As far as I can tell, the functionality introduced by @jacksonj04 in #16 only allows us to remove a **qualifier** — i.e. you can't apply it to the whole statement via, for example
```
Q61943707	-P39	Q61943707-B9266EA2-60A4-4B81-8347-474B9E8A30A3
```

It would be useful to also be able to remove the entire statement like that (perhaps only where there are no qualifiers on it)