New commitment structure

[lploom]

#80 #94
Changed commitment structure and hashing to match the spec.

Most notable changes in public data structures:

• rename "get_block_commitments" RPC to "get_block_records"
• rename "commitments" field to "aggregatorRecords" in "get_block_records" response
• rename "submit_commitment" RPC to "certification_request"
• rename "CommitmentRequest" to "CertificationRequest"
• rename "requestID" to "stateID"
• rename "Authenticator" to "CertificationData"
• rename "StateHash" to "SourceStateHash" in Authenticator
• remove "Algorithm" field from Authenticator
• move "TransactionHash" field from "CommitmentRequest" to "Authenticator"
• remove "request" field from Receipt
• new signature data definition: H(CBOR array [SourceStateHash, TransactionHash]) (without algorithm prefix)
• new stateID hash definition: H(CBOR array [SourceStateHash, PublicKey]) (with algorithm prefix)
• new leaf hash definition: H(CBOR array [PublicKey, SourceStateHash, TransactionHash, Signature]) (with algorithm prefix)

Internally commitment is still used e.g. commitment storage still remains etc. There's ~1000 references for "commitment" remaining which did not seem feasible to change. Externally there should be no more references for a "commitment".

Needs to be tested for regressions and compatibility with SDKs.