Add a setTermNet method in SNLInstance

[xtofalex]

Following SNLBusTerm setNet method, purpose of this enhancement is to add a setTermNet method in SNLInstance, this method will avoid to connect all bits of a term to a net, provided that both have the same size.

SNLInstance* ins1;
SNLDesign* model1 = ins1->getModel();
SNLBusTerm* model1Term = model1->getBusTerm(term1Name);
SNLInstance* ins2;
SNLDesign* model2 = ins2->getModel();
SNLBusTerm* model2Term = model2->getBusTerm(term2Name);
SNLBusNet* net = SNLBusNet::create(currentDesign, model1Term->getMSB(), model1Term->getLSB());
ins1->setTermNet(model1Term,  net);
ins2->setTermNet(model2Term,  net);

ins1 and ins2 terms will be connected if model1Term, model2Term and net share the same size.