Support different number systems

[voltrevo]

At the moment we assume a traditional arithmetic over u32.

Instead we should define a Number trait and allow the user to specify the number system they are using. Additionally we can provide implementations of common number systems.

trait Number {
    fn op(&self, op: Operation, rhs: &Self) -> Self;
    // note: we may want to separate this as prefix_op, infix_op, but that's a separate issue
}

then anything implementing this trait can be used by using it as the constraint on a generic, like this:

fn execute<N: Number>(&self, inputs: &[N]) -> Result<Vec<N>, CircuitError>