External accounts implemented for issue #5640

[r001]

This is the reopen of PR #6007.
External acccounts allow Metamask to track account whose private keys are stored on a safe device, and tx data and signatures are exchanged by using QR codes. This allows very safe account password storage.

This pull request enables users to create so called external accounts. This means that after applying this pull request in the "import account" menu there will be an "external" tab that enables importing an ethereum address. There is no local private key stored, but upon confirming a transaction a QR code is presented and the transaction can be signed by an external signer. And the signature can be provided in the signature input field. By providing the signature, the transaction will be signed, and published.

The way it works is the following:

1. User creates transaction (or msg signing) and Confirms it.
2. Request goes to the background, and since the from-accunt belongs to eth-external-account-keyring, the keyrings signTransaction() function is called.
3. Sign transaction adds an object to eth-keyring-controller's extToSign array, which is monitored by the UI modal.js base component.
4. Since there is a new extToSign entry ui/app/components/modals/modal.js starts the external-sign-modal.js window, and displays QR code, and requests signature.
5. Once signature received from user, the tx is segned normall, and handled in a standard way by Metamask.

To allow for external signatures, eth-keyring-controller package had to be updated, and eth-external-account-keyring package was created. So in the package.json my updated ones are the sources.
Eth-external-account-keyring is available at:
https://github.com/r001/eth-external-account-keyring

Install instructions for reference implementation of encoding/decoding QR code can be found at
https://github.com/r001/qr-encoding/blob/master/INSTALL.md

Modified signer that can create appropriate signature can be found at :
https://github.com/r001/dapptools/tree/ethsign-signature
To create signature use ethsign tx --signature-only <tx options>...

[r001]

@tmashuang This is the followup of PR #6007 . Sorry I could not reopen the issue.
I have implemented Parity Signer and ERC67 style of signing too. I will be doing some bugfixes that you have suggested and then we are ready to merge it I hope.

[r001]

@caffeinum I have implemented both Parity Signer, and ERC67 types of signing for external accounts in Metamask.

[r001]

I would need some help with css styling: "Sign with" dropdown should be placed over "signature" input. The problem is that the "sign with" puts his dropdown under "signaturee" input because of some weird zIndex stuff. Also the dropdowns should be of equal size. And different screensizes should be applied to QR code size. The QR code should be sized as large as possible.

[r001]

Some additional tests would be also nice to have.

[caffeinum]

@r001 why'd you close?

[r001]

@caffeinum you can find the new one here: PR #6267
BTW I keep screwing with the rebasing with git: if I don't rebase, then tests fail, if I do rebase and recreate the whole branch it gets closed here, if I force push then only the very last commit will contain the rebase the previous ones do not, this way you can't really roll back, only if you do another rebase yourself. But now I will just use force push, and the PR #6267 wont't be closed until it is either rejected or accepted by the team.