Make sure we split accents and boxes too.

Summary:
Doh.  Getting the active langauge list doesn't get accents and boxes
too.  So I've got back to listing it and just filtering out any rest.po
or datastore.po.  I don't have to special case empty because it is
always split up already and we never recreate it.

Test Plan:
touch intl/translations/accents.po
ls -1 intl/translations/pofiles | grep '^[^\.]*\.*.po$' \
        | sed 's/\..*//' | sort -u
See that it only lists "accents"

Reviewers: csilvers

Reviewed By: csilvers

Differential Revision: http://phabricator.khanacademy.org/D14563