Use export.lastLocale before UI locale if none specified
Use export.lastLocale before UI locale if none specified

This allows existing documents created before 4.0.27 with a
bibliographyLocale set to continue to use that value by default.

More details:

https://github.com/zotero/zotero/pull/795#issuecomment-120227051

retorquere/zotero,adunning/zotero,LinuxMercedes/zotero,hoehnp/zotero,hoehnp/zotero,sendecomp/zotero,gracile-fr/zotero,retorquere/zotero,sendecomp/zotero,rmzelle/zotero,rmzelle/zotero,hoehnp/zotero,retorquere/zotero,gracile-fr/zotero,adunning/zotero,robamler/zotero,robamler/zotero,gracile-fr/zotero,sendecomp/zotero,LinuxMercedes/zotero,rmzelle/zotero,robamler/zotero,adunning/zotero,LinuxMercedes/zotero