Add support for __profile__ to conduit calls.

Summary:
__profile__ is a 'global' setting, unlike the other arguments to
conduit calls which are per-call settings.  So I had to add support
for global settings to conduit.  But it wasn't that bad.

Test Plan:
Ran
   ./update_phabricator_repositories.py -n /tmp
and it completed successfully with 0 adds or deletes, showing the the
conduit call gave the normal results even after this change.

Reviewers: alpert

Reviewed By: alpert

Differential Revision: http://phabricator.khanacademy.org/D9969