- Add SignerPod.id computation (integrate kvs with MerkleTree).
- Updates frontend::SignerPod to be a wrapper on top of
backend::SignerPod with extra metadata (a keymap between hashes and
their strings).
- Get's rid of SignerPod.compile() since now the frontend::SignerPod
uses the method `::new()` which internally calls
backend::SignerPod::new which constructs the merkletree to use it's root
as PodID.
Add initial MerkleTree implementation, which is a wrapper on top of
Plonky2's MerkleTree, with the idea that the future iteration will
replace it by the MerkleTree specified at
https://0xparc.github.io/pod2/merkletree.html .
