Laying out the windows in the window manager frame, is a very similar
process regardless of doing it horizontally or vertically. So the
template design pattern was applied and the general functionality was
pulled up; only specific functionalities were put into the corresponding
classes.
kNCursesDemoApp: Separated the screen into three windows vertically. The
top and bottom window contain another two windows each, lay out
horizontally. The top left window is fixed to width 1 and the top right
takes the rest of the space. Bottom two windows take 50 % of the space
each.
Remarks: There are still some rendering bugs, when hiding and showing
windows. E. g. when hiding the top or middle window with `<F1>` or
`<F2>` respectively, the bottom window has some errors. Maybe some
timing issue.
Christian Burger