Allow Conduit method call logs to be exported with the standard export pipeline

Summary:
See PHI1026. Allow installs to export Conduit call logs to a flat format.

Also, add date range queries.

Test Plan:

• Exported some call logs.
• Filtered logs by date.

Reviewers: amckinley

Reviewed By: amckinley

Differential Revision: https://secure.phabricator.com/D19996