Rename ConnectorUnit.model_name to for_model_name
Rename ConnectorUnit.model_name to for_model_name

Because 'model_name' contains the name of the model we are working in in the
ConnectorEnvironment, and this 'model_name' represents the list of models on
which a ConnectorUnit can be used.

This is too confusing, especially since ConnectorUnit.model_name is hardly used

fevxie/connector,MindAndGo/connector,fevxie/connector,sylvain-garancher/connector,Endika/connector,hugosantosred/connector,brain-tec/connector,mohamedhagag/connector,BT-fgarbely/connector,js-landoo/connector,brain-tec/connector,js-landoo/connector,esousy/connector,mohamedhagag/connector,hugosantosred/connector,Antiun/connector,BT-jmichaud/connector,BT-ojossen/connector,sylvain-garancher/connector,maljac/connector,open-synergy/connector,Antiun/connector,dvitme/connector,acsone/connector,anybox/connector,BT-ojossen/connector,gurneyalex/connector,acsone/connector,BT-fgarbely/connector,zhaohuaw/connector,dvitme/connector,gurneyalex/connector,anybox/connector,Endika/connector,brain-tec/connector,MindAndGo/connector,zhaohuaw/connector,BT-jmichaud/connector,open-synergy/connector,maljac/connector,esousy/connector,acsone/connector