Added @since and @author in the header documentation

Usually the message should be always shown, but I think there there are some exceptions.

Hi, you are right, I did not realize a bit of mess in between my revisions.

little clean up

Removed unused parameter for toggleMenuBar()

Removed unused parameter in toggleShowMenuBar()

Thank you very much,

Added remainder message box with keyboard shortcut, to have back the menu bar.

Hi Nathaniel, thanks for all the support.
I can understand and agree with your concerns.
Not sure but maybe an option could be to add the hide menu bar entry in the setting menu via kxmlguiwindow and another entry to unhide it maybe can be putted in the context menu on the window title bar.
Just an idea, that requires wider discussions and knowledges.

Thank you, for all the feedback.