Fix/daef 301 Importing a wallet from a file

[tomislavhoracek]

This PR introduces integration of "wallet name" field and updated API endpoint for importing wallet.

TODOs

• Inject working default-wallet.json file to be used in acceptance tests
• Inspect acceptance tests (currently import-wallet acceptance test are failing due to the fact that current import endpoint doesn't accept .key files)
• Once API endpoint is updated check if importBackupJSON endpoint flow-type declaration is correct: API update delayed

declare function importBackupJSON(tls: TlsConfig, filePath: string, walletPassword: ?string, walletName: ?string): Promise<ApiWallet>;

• Inject updated Japanese translation (on import dialog label for wallet file has been changed from "Upload your key file" to "Import file")

"wallet.file.import.dialog.walletFileLabel": "Import file"

• Make sure this feature is working both with wallet JSON and wallet key file after API has been updated API update delayed
• Handle imports of both .key and .json files in the Front-End
• Add error handling for 'Wallet already imported' case - this is error response for that case:

Wallet with id LaVWX1....V2UtYartph9kL already exists

• Inject missing/updated Japanese translations:

"api.errors.WalletAlreadyImportedError": "Wallet you are trying to import already exists."
"api.errors.WalletAlreadyRestoredError": "Wallet you are trying to restore already exists."
"api.errors.WalletFileImportError": "Wallet could not be imported, please make sure you are providing a correct file."
"wallet.add.dialog.import.description": "Import wallet from a file"

[darko-mijic]

Looks great! And it works. ;)