models: Add 'project' field to Series

models: Add 'project' field to Series

This is helpful for filtering. We use RunPython because folks are likely
to have few if any Series objects existing yet. In addition, we update
the unique constraints for SeriesReference as it's now possible to
handle messages with duplicate message IDs.

The update is included in parser to ensure this applies immediately.

Signed-off-by: Stephen Finucane <stephen@that.guru>
Reviewed-by: Andy Doan <andy.doan@linaro.org>