Clarify how multisig is used (with particular focus on paper wallet)

[sashafklein]

I wasn't sure I understood the manner in which the paper wallet fits into the quorum, or exactly what information needed to be saved where.

Figured that the best way to clarify was in a pull request that would clarify for other readers (if I'm correct).

I also added a high-level How it Works page to clarify usage flows as far as I understand them. Again, this is an exercise in exposing my (lack of) understanding, and turning that into hopefully useful explanation.

[mflaxman]

Thanks for the PR @sashafklein!

At this point, there are enough other signers (Passport, BB02, multiwallet, bluewallet, Jade, ledger?, etc) that I'm going to re-write the guide as a choose-your-own devices guide. Paper wallets will remain a viable option for recovery only, but they're no longer going to remain the default.

[dykstranet]

I would like to see clarification too on using a seedpicker paper wallet in a quorum. It's not clear what wallets support import of the seedpicker words. I was not able to import these words into electrum and other Bip39 wallets to test the recovery process. (This was attempted on testnet with seedpicker and specter desktop )