Wallet improvements
This issue contains a list of improvements in the wallet area (wallet operations, UI/UX):

- [x] Add ability to create wallet right via the admin interface, display the seed and (optionally) create a wallet by using xpub only
- [ ] Hardware wallet support
- [x] More utilities (check electrum commands/features and implement them in the UI)
- [x] Better wallet handling in case of disabling/enabling new currencies
- [x] Improve wallet processing, reduce sync times (maybe re-consider current approach and consider the fact that the daemon might be syncing, it takes a bit of time, or that the wallet is large, plus some daemons might be slower than others)
- [x] Avoid the cases when user is unable to edit wallets because of invalid xpub entered somehow/disabled currency/daemon unavailable
- [x] In continuation: currently, on server startup, user must wait quite some time for all wallets to load to get access to the wallets page, server stats and invoice creation
- [x] Check BIP39 support/whether it's supported by `restore` function in electrum
- [ ] Also test all the code for BCH, depends on Electron-Cash/Electron-Cash#2319
- [x] Ethereum support (#105)
- [x] Monero support