some fixes noticed during today's discussion around refs #302

* move hotkey settings in own GUI component -> easier adjustments
* some fixes for dock widgets when tab widget is shown without names (unrelated but found + fixed in same step)

src/blackgui/dockwidget.h

@@ -73,6 +73,9 @@ namespace BlackGui
         //! Window title backup
         const QString &windowTitleBackup() const { return this->m_windowTitleBackup; }
 
+        //! If current window title is empty, use backup
+        QString windowTitleOrBackup() const;
+
         //! Window title when window is docked
         bool showTitleWhenDocked() const { return this->m_windowTitleWhenDocked; }