feature_required_back leads to ambiguous function calls

[tonimueller]

For feature FeatureConnectionSc.h and excluded volume feature is needed. Maybe the user himself wants a specilized version of such a feature, e.g. only to LattiePowerOfTwo ... Now there is a problem if the one add the FeatureExcluedVolumeSc in the feature_required_back list of the FeatureConnectionSc.h because the feature List adds the specialized and the default excluded volume feature which both uses, e.g getLatticeEntry(). The program cannot decide which function to use (either from the specialized feature or the other one) ...
Seems that this is a nasty problem, which should be changed within the turning away from the LOKI-typelist which was already suggested @hrabbel in issue #57 .