add ability to detect and deal with showPNX.jsp extension of primo

don't break things on clean-up and add some more data fields for articles

[Primo] Use Zotero's ISBN and ISSN checking functions

[Primo] Support multiple URL schemes for PNX records.

[Primo] Restore @adam3smith's changes

add creators and try to add test
Merge pull request #617 from adam3smith/primojsp

detect and deal with showPNX.jsp extension of primo
[Primo] Fix typo and improve link xpath
fix multiples in EBSCOhost - leaving the old format in to be safe
[PubMed Central] Support PDF attachments in PubReader
Merge branch 'master' of git://github.com/zotero/translators
fix Stanford Encyclopedia of Philosophy
minor fixes to ACL Artefacts Canada AJC, and Beobachter
[EM] Support bib, bibo, and z namespaces for item types
e.g. <meta name="bibo.type" value="manuscript"/>
[EM] Undo z namespace part from ff5d47a4f2d8e8f91131c1833f61c3d611461a2c