Coils incompatible with most current supplies

The Coil and CoilPair components require a Switchable right now either through an extra argument or the current source must inherit from Switchable. I don't see the point here as all our current sources except the HBridgedCurrentSource are not Switchable. And the concept of a coil is not necessarily switchable and often just a standard current source without any switch is used to control coils. I see three options to fix this:

1. Make all current sources switchable (implement on/off by setting the current to zero and back to value before)
2. Remove the Switchable capability from the Coil and add if necessary a SwitchableCoil
3. Implement the logic in Coil (on/off by setting the current to zero and back to value before if the current supply is not switchable/ no switch supplied)

I think the first way would be the most general and would prefer this.