fmss

Copperbox revision 2496.

I've added a second monad which supports variable binding - this is so a single envelope declaration can be shared by multiple oscillators.

I've called the new monad Spec which was the name I used yesterday for the other monad. Yesterday's monad is now called Config. Config is the patching of oscillators cf. an algorithm in DX7 terminology. Spec is an FM instrument that instantiates a Config with particular oscillators.