Issue: http://code.google.com/p/pharo/issues/detail?id=5629
This enhancement adds possibility to create window group from any system window. It is slightly modified version of Laurent code published in the thread "GroupWindowMorph that can embed any kind of window as tab". system modifications: - adds option "Create window group" to the window menu modifications to the original code: - accept drops only on tabs - move the class to the Category "Morphic-Windows" -- Pavel
