- Closes AC-1302.
- Generalizes authority:
  - Accounts are governed by authorities
  - An authority has signers
  - A signer has key entries
- Replaces `AuthDisabled`, `KeyBook`, and `ManagerKeyBook` with `AccountAuth [](URL, Disabled)`
- Removes the account header
- Most accounts now have `AccountAuth`
- Lite token accounts are their own authority
- Key pages are governed by the authority of the book they belong to - key pages cannot have their own auth rules.
- Lite identities and lite data accounts are not governed.