Automatically remove annotations that point to non-existing argumentIds

A UIMA Annotation type that extends String could be used (clean, but forces the cleanup to happen within the two parts of the assessment step). Or some specific context-name-suffix.

Problem is: this breaks streaming, as the complete list of final arguments is required.

Doing such a step of cleaning might be helpful after both mining and assessment, actually.

Having such dead links in our data is just irritating.