Checks for a negative interaction. NB This will have to be done using SQL otherwise we end up materializing all
interactions just to do the check.
Also the new intact curation rules specify that an Experiment should ONLY contain negative Interactions if it is
annotated as 'negative'. Thus to decide if an Experiment is classified as 'negative', the Annotations of that
Experiment need to be checked for one with a 'negative' Controlled Vocab attached to it as a topic.
However at some point in the future there may be a possibility that only the Interactions will be marked as
'negative' (not the Experiment), and so these should be checked also, with duplicate matches being ignored.
This method has to be static because it is called by the static 'classifyExperiments'.