cardlist

Hi Al.

I have prepared a small patch that makes CARD_LIST polymorphic.
The patch makes ~CARD_LIST as well as insert/erase virtual.

I believe there are features that require difficult changes, but could
well be implemented as subclasses and included with plugins. One such
feature is fast/mapped lookup without linear search. This map and
similar tweaks could be used in user interface plugins that would
otherwise require a different CARD_LIST.

NB: This is independent but related to the scope issue. The scope-2
branch essentially changes plugins, while this new one is a header
change.

Thanks
felix