Reusing concerns without RAM models

[Berk Duran]

Currently, when reusing a concern that does not have any realizing models, TouchCore gives the following (BadConfiguration) error upon "Save".

In order to save the concern reuse, at least an empty realizing model must be created for the concern to be reused.

[Matthias Schoettle]

I think COREWeaver needs to be refactored to not take a set of Aspect as a parameter. Instead weaveSelectedFeatures should take the selected features as the name indicates.