Standards for Multisig Recovery

[ChristopherA]

Related to #72 is we need better standards for multisig recovery. I know several people that were not able to get Green Addresses multisig recovery to work, and most people don't know that to recover requires more than just the seed words, but also the xpub descriptors, and possibly some credentials auth recovery of a co-signer service.

With current bitcoin multisig can also be more complex to recovery given time-locks, covenant vaults, delegated signatures, various RBF/CPFP schemes, etc. With taproot, we'll also have offline signing schemes that might need different approaches than descriptors to describe the spend policies.

-- Christopher Allen