Relax skip condition for values in RoI metric
Relax skip condition for values in RoI metric

It was not okay to set the skip condition to blank? for values in the
Richness of Information metric. This only applies for strings. Hence,
I have added my own skip? method which is sensitive to this piece of
information.

Signed-off-by: Konrad Reiche <4ff0213f56e2082fcd8c882d04c546881c579ce4@gmail.com>

platzhirsch/metadata-census