Experimenting let me stumble over problems with the
static methods involved when wanting to derive from
an existing Item:: implementation. Both cases
(1) derive and add local data
(2) derive to get a new class/identifier
had problems. Experimented and decided to take an
approach closer to have a service-structure per
derivation that e.g. allows re-usage of the Item-
Administrator in case (2). Case (2) is important in
potentially solving the ItemSet/SlotSet mix I currently
have by allowing simple definition of Items derived from
simple basic types (as e.g. CntOUString) to have a
solution for Items that now have to go to Slots.

Change-Id: Ibe1d8d967614e07de65bd81d59e36681e50687b6