ChildGenerator is used to generate VisualObjects with
a view descriptor.  It comes with some methods 'generate'
and 'operator ()' that perform this generation, overloaded
for UI_CompositeVObjects and UI_VObjCollections as
client.  The code of the method createChild has been copied
from UI_CompositeVObject and extended for new types.
The ViewType constants needed for these new types are contained
in 'newtypes.h'.  There are also some methods 'appendXXX', that
append the new children at the bottom/top/left/right =: XXX.

