There was some problems with restore, hide, clean and save background of item parts,
seen in detailsline. kill() worked not really clean.
kill() works now as virtual member and uses paintBackgroundBoxRel().
In consequence of which:
-unnecessary members in subclasses removed.
-add some comments
Pointer is typically of type CComponentsForm or derived classes,
default intialized with NULL and serves to access for
properties of parent object by embedded items.
If items are used in forms it can be usefully to have a variable
which contains the real position on screen.
This can happen e.g. if an item contains separate render methods, because within forms
usual x/y values related to form dimensions and be converted.
It's easier to work with smaller files.
Most files contain only one cc-class and their names are
derived on the particular class that is contained therein.
