The primary thing this does is to introduce a SelectionNameSvc that
tracks the name of all the selection bits as reported by the various
selection tools, allowing to give much better labels for the
individual bins in the selection.  In addition this means I no longer
need to track the bits for each selection mask, as they get
automatically tracked.

I also added a configuration block for the cut flows (there wasn't one
yet), that allows to neatly add the cut flows when added.

The one breaking change is that this now requires a SelectionNameSvc
to get created.  I hope this doesn't cause too many issues.  In order
to minimize the effect of such changes in the future I introduced a
CommonServicesBlock (and corresponding sequence), to which I can add
more services as needed.