Plumb ivysettings.xml location to the publish template.

Testing Done:
1.) tests including publish integration
==
$ PANTS_DEV=1 ./pants goal test tests/python/pants_test/::

2.) local publish
==
$ yes | PANTS_DEV=1 ./pants goal publish src/{java,scala}:: --no-publish-dryrun --publish-local=/tmp/repo --doc-javadoc-ignore-failure --doc-scaladoc-ignore-failure

Bugs closed: 400

Reviewed at https://rbcommons.com/s/twitter/r/764/