Creator sequence breaks in RDF export with > 10 creators

[fbennett]

Wading into sort issues here again, watch out. :)

Exporting an importing an item with ten or more authors breaks the sequence, such that reimporting the item yields a different sequence of authors than the original item:

​http://forums.zotero.org/discussion/14585/bug-report-multiple-authors-in-wrong-order-after-exportimport/#Comment_71974

The RDF serialization method performs a sort that seems to rely on the uri of the predicate. This contains the sequence number of items in the list as an unpadded string suffix, with the expected result when the list of strings is sorted.

The attached patch splits the uri and sorts independently on the base uri (as a string) and the suffix (as a number). It wants further testing, it assumes that the suffix will always be numeric, and may not be the best or the right fix, but it may provide a basis for a short-term fix.

[simon]

(In [6998]) closes #1732, Creator sequence breaks in RDF export with > 10 creators (thanks Frank)