[FIX] MoreUnimpRemovalsAndFixes-nk ( [er][et] seems ok )

[Alexander at Lazarevic.de]

Browsed the code and just verified that the removed methods and message
sends are either never used or are not implemented at all
(subClassResponsibility is a good one). The only thing I'm not sure
about is removing mouseMove: from MenuItemMorph, but I haven't tried to
hard to see why this is superfluous. After fileIn menus still work as
they used to, so I guess it is ok.