message: return backupWallet functionality
diff: @@ -401,6 +401,7 @@ void BitcoinGUI::createActions()
  if(walletFrame)
  {
  connect(encryptWalletAction, &QAction::triggered, walletFrame, &WalletFrame::encryptWallet);
  + connect(backupWalletAction, &QAction::triggered, walletFrame, &WalletFrame::backupWallet);
  connect(decryptForMintingAction, &QAction::triggered, walletFrame, &WalletFrame::decryptForMinting);
  connect(changePassphraseAction, &QAction::triggered, walletFrame, &WalletFrame::changePassphrase);
  connect(signMessageAction, &QAction::triggered, [this]{ showNormalIfMinimized(); });
  