CMSPixelProducer: use different EVENT_TYPE identifiers for DUT and REF
detectors - currently the only way to have two completely independent
converter plugins.
CMSPixelConverter: some more workarounds for eudaq not being able
to separate datastreams from two detectors of the same kind: create
three converter plugins for CMSPixel, CMSPixelDUT, CMSPixelREF which
all have their own instance of CMSPixelHelper to do the decoding work.