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/walletview.h

@@ -105,6 +105,9 @@ public slots:
 signals:
     /** Signal that we want to show the main window */
     void showNormalIfMinimized();
+
+    /**  Fired when a message should be reported to the user */
+    void message(const QString &title, const QString &message, unsigned int style);
 };
 
 #endif // WALLETVIEW_H