Warn individually only if told to do so

This lets us fail on too many, but warn on each.
Okay, so I was thinking of achieving this:

* Fail when maxTodos is exceeded
* Warn when Todo exists

So we could have two instantiations, one with priority 1, that sets a reasonable maxTodos (this fails the build) and another with priority 3, that adds a violation on every Todo so it shows up on the static analysis report (the build passes but has a warning). Seeing as all violations within an instance of a rule are at the same priority, it looks like we'd have to do this.