[Qt] Rework of payment request UI (mainly for insecure pr)

- this shows insecure (unsecured) payment requests in a new yellowish
  colored UI (based on the secure payment request UI) instead of our
  normal payment UI
- allows us to receive paymentACK messages for insecure payment requests
- allows us to handle expirations for insecure payment request
- changed walletmodel, so that all types of payment requests don't touch
  the addressbook

src/qt/walletmodel.cpp

@@ -258,8 +258,8 @@ WalletModel::SendCoinsReturn WalletModel::sendCoins(WalletModelTransaction &tran
     // and emit coinsSent signal for each recipient
     foreach(const SendCoinsRecipient &rcp, transaction.getRecipients())
     {
-        // Don't touch the address book when we have a secure payment-request
-        if (rcp.authenticatedMerchant.isEmpty())
+        // Don't touch the address book when we have a payment request
+        if (!rcp.paymentRequest.IsInitialized())
         {
             std::string strAddress = rcp.address.toStdString();
             CTxDestination dest = CBitcoinAddress(strAddress).Get();