- Add option to import a Parity Signer account. It is then stored in
local storage.

- Send transactions with Parity Signer accounts

- Refactor sendStore so that "token" (and chainId) is inside this.tx;
avoids having to pass `token` around every function, and it makes sense
to put it in the object since it is part of the tx info.

- Add account type (either node or signer) to accountsInfo

- Add account type to withAccount; output props are now `{account:
{address, type}}` instead of `{accountAddress}`

* Create TxDetails component and move relevant instance methods from TxForm into TxDetails

* Fix linting warning `Using target="_blank" without rel="noopener noreferrer" is a security risk: see https://mathiasbynens.github.io/rel-noopener`