Implemented application login.

Minor UI improvement.
Fixed memory leaks.

application/mainwindow.h

@@ -2,6 +2,9 @@
 #define MAINWINDOW_H
 
 #include <QMainWindow>
+#include <QLabel>
+
+#include "logindialog.h"
 
 #define PLUGIN_INDEX "plug_index"
 
@@ -25,8 +28,16 @@ private slots:
 
     void on_tabWidget_tabCloseRequested(int index);
 
+    void on_actionLogin_triggered();
+
 private:
     Ui::MainWindow *ui;
+    LoginDialog *m_loginDialog;
+    QLabel *m_lblUser;
+
+    // QWidget interface
+protected:
+    void showEvent(QShowEvent *evt);
 };
 
 #endif // MAINWINDOW_H