Request: fully-encapsulating binary backup/restore format

The process of backing up and restoring a Specter Desktop is error prone. As a user, it's easy to imagine that the printed QR codes is enough, but when dealing with multisig there is metadata that must be carefully managed to transition to a new Specter Desktop.

One way to improve this would be to add support for an backup/restore binary format that allowed for rich data structure representation. This would open the door to storing *everything* needed to *entirely* backup Specter, and restore it, using one file, now and forever.

Types of metadata that could be included:

* Derivation paths
* Public keys
* Labels
* Hot wallet .dat

Example binary transports that can be used to aid in developing the format:

* Protobuf
* Thrift
* Avro

Does this make sense? As someone who practices his backup/restore process regularly, I can tell you that noobs most certainly will have a problem maneuvering a successful multisig backup/restore.

PS: Specter is incredible.