TPAC: record/authors.tt2 duplicates author / credited credits

[Dan Scott]

* Evergreen master

The credits list for TPAC record details is fairly dumb at the moment - to the extent that the XPath for the "Author" and "Credited" types are duplicated and the output reflects it.

Perhaps "Credited" was meant to be a less book-centric replacement for "Author" or "Added Author"?

In any case, this function should be taught to:

1. Check for and use relator codes (http://www.loc.gov/marc/relators/) from the $4 - we can automatically extract the code -> term relationships;
2. Fall back to the $e if there is no explicit relator code;
3. Use finer-grained XPath; for example, field 100 is non-repeatable according to http://www.loc.gov/marc/bibliographic/bd100.html - which, given different types of materials such as books and movies and music, suggests that we should use a generic term such as "Primary content creator" for the 1xx field and (in the absence of explicit relator codes) "Other content creator" or "Credited" for 7xx fields

[Dan Scott (denials)]

Fixed via commit 06ea5ec9b641bb