Check whether we need all of the multiplier classes for SMG model checker

[TheGreatfpmK]

I noticed we have some possibly duplicate code in Payntbind which we could instead use directly from Storm.

More precisely the Multiplier/NativeMultiplier/GmmxxMultiplier classes (note GmmxxMultiplier was recently renamed in Storm). We should check this and if it's indeed redundant code we should use the code in Storm.

I will check it together with @PurpleDragon64 once there is time.

[TheGreatfpmK]

We cannot really use the code in Storm as these classes include the core of robust VI which is not in Storm currently. I've updated most of the classes to the barebones code we actually need, but I'm not sure if we can safely remove more of the code here and this should still be investigated.