Add publisher location to JATS

[asmecher]

Describe the bug From the Coalition Publica metadata recommendations: add publisher location to JATS.

This data is currently available in the Citation Style Language plugin settings:

...and more broadly (just country level) in Settings > Journal > Masthead:

[asmecher]

Content model:

<publisher>
    <publisher-name>Public Knowledge Project</publisher-name>
    <publisher-loc>London, UK
        <country>IS</country>
        <uri>http://www.google.com</uri>
    </publisher-loc>
</publisher> 

The London, UK value comes from Citation Style Language plugin settings; the country and URL come from the journal masthead settings.