Use Witness Data generated by IAVL tree in Deep Subtrees

[Manav-Aggarwal]

We'd like to be able to load Witness Data generated in #19 in a Deep Subtree and later on be able to perform all operations recorded in the Witness Data.

When an operation is performed on the Deep Subtree, it should first check that the operation matches the current operation in the Witness Data that hasn't been performed. Also, we should verify all the existence proofs inside the Witness Data to make sure they match up with the root hash of the Deep Subtree at any point.

Parent issue: #19