more backends: ark halo2 dusk besides bellman?

[lispc]

ark ref:

https://github.com/gakonst/ark-circom
https://github.com/rust-zkp/ark-plonk

[0xmountaintop]

halo2 uses a different commitment scheme from the original plonk paper. and the verifier smart contract will be different