Dear All,

this is the first item in a series of oc-csl patches which I've
accumulated and am planning to send this week. (My first attempt to
send a patch, so please be patient and forgiving :-) )

This particular change removes the itemgetter constructor function
defined in oc-csl.el and uses the one now provided by citeproc-el
which has the same functionality but also supports org-bibtex
bibliographies. In addition to being a bit more featureful this change
also avoids unnecessary code duplication.

best wishes,
András