Update Primo.js

Improve handling for pages, see https://forums.zotero.org/discussion/33862/princeton-primo-translator/#Comment_200487 , in the following order
 1. prefers spage, epage if both are given
 2. prefers overallPage if only one of spage or epage or none are given
 3. will use just spage, or just epage if this is only given
>at least if this is really just the end page

How likely is that? Could it be just a single page article? I mean... who would enter only the end page in the database?

>But could we have buggy data with the whole page range in one of these tags?

Good point. Though in that case (if we omit the leading/trailing dash) we would probably be ok, since I doubt it would be replicated in other fields.

>shouldn't this be '–' rather than '-'

Yes, it should