the skip/retain/recalc handlign was confusing. This removes the switcheroo between leveled_codec and leveled_iclerk when mkaing the decision.
Also now the building of the accumulator is handled efficiently (not using ++ on the list).
Tried to rmeove as much of ?HEAD tag handling from leveled_head - as we want leveled_head to be only concerned with the head manipulation for object tags (?STD, ?RIAK and user-defined).
To allow for extraction of metadata, and building of head responses - it should eb possible to dynamically and user-defined tags, and functions to treat them.
If no function is defined, revert to the behaviour of the ?STD tag.
More obvious how to extend the code as it is all in one module.
Also add a new field to the standard object metadata tuple that may hold in the future other object metadata base don user-defined functions.
