(Feature) Simultaneous support of Trezor and Ledger HD wallets

[vbaranov]

Problem: On switching from one HD wallet to another, for example, switching from Ledger to Trezor or vise-versa, accounts from forgotten HD device are automatically lost in the list of imported accounts.

Solution: This PR switches on the simultaneous support of Trezor and Ledger HD wallets. It means, that users will be able to work in Nifty wallet with Ledger and Trezor accounts simultaneously.

How simultaneous support of Trezor/Ledger will work:
When you are switching from one HD device to another, you should click Forget this device, as usual. The new thing, that is introduced in this PR, that the confirmation page will be opened with the checkbox Are you sure you want to forget this Ledger/Trezor?. It will be unchecked by default.

• if checkbox will be unchecked, then accounts from forgotten device will not be removed from the imported accounts list. And users will be able to operate from these accounts (send transactions, interact with smart-contracts etc).
• if checkbox will be checked, then accounts from forgotten will be removed, as it worked before this PR.

How confirmation page looks like:

Built on top of #250