Move .confirm javascript to a separate, properly enqueued file

This improves our compliance with WP standards, improves our integration with
caching systems, and allows plugins to manage the conditional loading of
scripts.

Fixes #5209

git-svn-id: https://buddypress.svn.wordpress.org/trunk@8091 cdf35c40-ae34-48e0-9cc9-0c9da1808c22