allow emit message() in sendcoinsdialog and walletview

- this allows us to use emit message() over MessageBox:: or gui->message()
  calls in sendcoinsdialog and walletview
- move main handlePaymentRequest() functionality back to BitcoinGUI
- move a showNormalIfMinimized() before gotoSendCoinsPage()

src/qt/bitcoingui.h

@@ -146,7 +146,7 @@ public slots:
     */
     void askFee(qint64 nFeeRequired, bool *payFee);
 
-    void handlePaymentRequest(const SendCoinsRecipient& recipient);
+    bool handlePaymentRequest(const SendCoinsRecipient& recipient);
 
     /** Show incoming transaction notification for new transactions. */
     void incomingTransaction(const QString& date, int unit, qint64 amount, const QString& type, const QString& address);