GUI: merge sign/verify message into a single window with tabbed UI

- add UI-feedback via QValidatedLineEdit
- copy button for generated signature was moved to the signature output field
- add an addressbook button to verify message tab
- input fields are now evenly ordered for sign and verify tabs
- update FIRST_CLASS_MESSAGING support to ensure a good UX
- add a button and context menu entry in addressbook for verify message (to be consistent with sign message)
- focus is now only set/changed, when clearing input fields or adding an address via addressbook
- re-work / update some strings
- ensure model gets initialized in the SignVerifyMessageDialog constructor
- add checks for a valid model to both addressbook buttons
- remove unneeded includes for Qt GUI elements that are listed in ui_signverifymessagedialog.h anyway

src/qt/bitcoingui.h

@@ -11,7 +11,7 @@ class TransactionView;
 class OverviewPage;
 class AddressBookPage;
 class SendCoinsDialog;
-class MessagePage;
+class SignVerifyMessageDialog;
 class Notificator;
 class RPCConsole;
 
@@ -64,7 +64,7 @@ private:
     AddressBookPage *addressBookPage;
     AddressBookPage *receiveCoinsPage;
     SendCoinsDialog *sendCoinsPage;
-    MessagePage *messagePage;
+    SignVerifyMessageDialog *signVerifyMessageDialog;
 
     QLabel *labelEncryptionIcon;
     QLabel *labelConnectionsIcon;
@@ -78,8 +78,9 @@ private:
     QAction *quitAction;
     QAction *sendCoinsAction;
     QAction *addressBookAction;
-    QAction *messageAction;
+    QAction *signMessageAction;
     QAction *verifyMessageAction;
+    QAction *firstClassMessagingAction;
     QAction *aboutAction;
     QAction *receiveCoinsAction;
     QAction *optionsAction;
@@ -131,7 +132,8 @@ public slots:
     void askFee(qint64 nFeeRequired, bool *payFee);
     void handleURI(QString strURI);
 
-    void gotoMessagePage(QString addr = "");
+    void gotoSignMessageTab(QString addr = "");
+    void gotoVerifyMessageTab(QString addr = "");
 
 private slots:
     /** Switch to overview (home) page */
@@ -164,8 +166,6 @@ private slots:
     void backupWallet();
     /** Change encrypted wallet passphrase */
     void changePassphrase();
-    /** Verify a message signature */
-    void verifyMessage();
     /** Ask for pass phrase to unlock wallet temporarily */
     void unlockWallet();