Use Feature::species() as the only source for species name
Created by: muffato
This would ease making Compara's ConstrainedElement a sub-class of Feature. ConstrainedElement's adaptor does not derive from BaseFeatureAdaptor. It is Compara's ConstrainedElementAdaptor which "species" is "Multi". With the proposed change in, we only have to override ConstrainedElement::species()