substrate encodings

[serapath]

@TODO

• SUBSTRATE ENCODING
  hash_number - should be named: index
  hash - should be named: hash.data
  total_length - should be named: size
• get rid of the field hashtype entirely and just have it internal to substrate, because it can be calculated/derived from other params
  // hash of the parent when used in calculation of the root hash doesn't contain hashtype
  // => because that's part of the hash payload in the first place
  // ==> hardcode hashtype to 2
  // ==> hashtype of the merkle root is always 2