Electrum instead of Bitcoin Core

[bayfitt]

Consider updating _docs/extend/improvements.md, because ... We should use Electrum instead of Bitcoin core because it has multisig, qr codes, and can be backed up with a seed phrase which can be written on paper. Also you can have an xpub which will generate an unlimited number of addresses. Electrum also comes preinstalled on tails, so only two usbs and two computers are needed.