Add extended_file_field integration

Mostly looks good on a quick visual inspection. A few minor nits:

+ return l(t('View details'), variable_get('pift_server', 'http://example.com') . 'pifr/test/' . check_plain($test_id));

A) l() already does check_plain() on the path, so the check_plain() call here (and nearby in the patch) is unnecessary (and in the bizzarre case that $test_id had an & or something, would lead to double-escaping and brokenness).

If $test_id is always supposed to be an int, you could cast it to an int here if you wanted to be extra careful, but again, not really needed. ;)

B) Is the pift_server setting supposed to have a trailing slash? Do we enforce that? If it's not defined, this would lead to a URL like http://example.compifr/test/1. Seems like we want
variable_get('pift_server', 'http://example.com') . '/pifr/test/' ... (with a leading slash in front of '/pifr/test/' no?

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The bigger question is how this integration will actually work on d.o -- namely, are we just doing N more columns in the attachments table, or are we trying to do a multi-row thing? If multi-row, how is that going to work? ;) And is any of this being configured on rebuilds (and if so, where)?

Thanks!
-Derek