Define serialization/deserialization functions for messages in the message layer

[hannahhoward]

In the message layer, define a FromNet_1_0 function and a ToNet_1_0 method on message

• we should maintain two maps of [peer + legacy requestID] -> UUID + UUID -> [peer + legacy requestID]

FromNet_1_0 algorithm:

• for each legacy ID in the message, check the peer+legacy -> UUID for an existing value. If not, generate a new UUID and write entries in both maps. Use existing UUID if present

ToNet_1_0 algorithm:

• for each UUID in the message, check the UUID -> peer+legacy ID map for an existing value. If not, generate the new UUID and write entries in both maps. Use existing Peer + legacy request ID if present.