instantiate model as slot, root references are broken

[rempel]

when a model is instantiated as a slot in another model, references to the previously main model using root.a now point to the wrong model (parent of intended model). this concerns global parameter in sbml import, which are addressed using this mechanism. to allow instantiation the reference should be changed to parent.(parent.)+.a should be changed in sbml import as the model should not be changed (parametrization would be another option, but might be to deep within the model) during instantiation.

[rempel]

there seems to be no simple solution for this as using slot-pathes with more than 2 elements does not work in all situations. disabling the checks results in drastic change of the syntax.