using Tk::IDElayout

[chrstphrchvz]

I came across the Tk::IDElayout module, which shares its maintainer with the Tcl::pTk module. It lets UI panes be rearranged freely as tab frames a window, as well as undocked to become its own window. (see Screenshots.pdf)

This seems like a very interesting module since only much newer GUI widget toolkits tend to provide this feature (e.g. QDockWidget in Qt, used by IDEs such as Spyder and Octave). I would be interested in adapting hsw12_gui to use this module if available, that way a single window can be used. ~~(That also works around the issue with the Tk 8-style menubar leaving extra space when in a window by itself.)~~