As smkettner states, there is no need to have any special switching involved with generator and solar controller. When the generator is operating, the solar controller will sense the higher DC current and limit by itself. The best solution is to have the solar system active at all times. If set correctly, the controller will keep your batteries charged better than a manual charger.
If you're still hesitant about this, install a manual circuit breaker (operates like a switch) between the panels and the controller. That will interrupt any power from the modules when in the "off" position.
I'd suggest that you do an energy audit and calculate your power needs. The addition of batteries is typically cheaper than the cost of fuel to run a generator. You don't have to listen to the generator, either. If 120V AC is needed, an inverter can supply that, also quietly, and without fuel supply.
