Binops integrated

[benjaminwilson]

Ryan's work implementing the binary operations AND and XOR has been ported over i.e. made to work with the new witnesses builders.

Also made some changes along the way:

• constant arguments to a bin op are now folded into the constraints matrix (rather than being injected as witnesses, along with their digital decomposition).
• the inputs and outputs of the bin op are now combined using a RS fingerprint (rather than using constant multipliers). This means that the inputs and outputs don't need to be range checked.