Port over ICS23 spec into v2 folder

[AdityaSripal]

ICS23 hasn't changed significantly from v2 to v1 though it is a confusing spec and is need of clarification and simplification.

Moreover the specific details of the confio implementation are not necessary so long as the client underlying an IBC connection is capable of verifying a proof of arbitrary bytes, given a path and value. Thus, the confio implementation and Merkle proof verification in general is a client-level detail. For example, 06-solomachine and 09-localhost do not make use of MerkleProofs even though they are IBC compliant.

Given this, does it make more sense to remove this spec or move it into an optional folder and leave the necessary items in ICS24?