Update UI through async calls MainFrameRepaint and AddressBookRepaint instead of a timer.

- Overall, this is better design
- This fixes problems with the address book UI not updating when the address book is changed through RPC
- Move Statusbar change detection responsibility to ClientModel

src/qt/bitcoingui.h

@@ -113,8 +113,6 @@ public slots:
        @see WalletModel::EncryptionStatus
     */
     void setEncryptionStatus(int status);
-    /** Set the status bar text if there are any warnings (removes sync progress bar if applicable) */
-    void refreshStatusBar();
 
     /** Notify the user of an error in the network or transaction handling code. */
     void error(const QString &title, const QString &message);