Feedback re: CBOR parsing, ensure all bytes are parsed

[CedarMist]

This was noted in an audit:

• the _decodeReceiptUndelegateDone function is the absence of a check to ensure that the parsing of the CBOR data structure hats-finance/Accumulated-finance-0x75278bcc0fa7c9e3af98654bce195eaf3bb6a784#60

There are a few issues around CBOR parsing in Solidity:

• If new keys are added in future to existing structures this could break contracts
  • A workaround for this, is passing in a 'schema version' argument, which returns different structures - e.g. request 'version 2' to return the struct with the new fields
• Implement a skipping CBOR parser, which skips past unknown keys