Date ranges, fuzzy dates, dates BCE

[fbennett]

Dates are in flux at the moment, with a firm desire in CSL circles to rely on the Library of Congress EDTF (Extended Date Time Format) standard, but with uncertainty over whether, when eventually finished, that standard will cover all of the use cases needed for rendering citations.

When EDTF becomes available, work will remain to build and test out revisions to the parsing module behind the Zotero UI, for the support of date ranges, fuzzy dates, and dates BCE.

As a first step toward that eventual goal, the attached patch (against the current trunk at r7344) supplies an option that will send the raw date string stored by Zotero to citeproc-js when formatting citations, for onward processing by the processor's own internal parsing module.

This isn't meant as a permanent solution, and I've given the option an ugly name to underline its temporary nature; but it does provide a channel for testing the parser behavior, against the day when agreement can be reached on a serialized date form suitable for data exchange and official recognition in a well specified CSL input format. If the parser proves sufficiently robust, it may also provide a solution for users who require support for these kinds of dates.