script to award theme reviewer points retroactively (bug 909985)


Runs well locally and on -dev. Well tested. Committing as script rather than migration this time - to run on prod in more controlled situation.

About 4000 objects to create.

Some optimizations have been made

- using ```bulk_create```
- removing ```get_or_create``` functionality.
- Celery tasks chunked to handle 1000 at a time to hog only a few workers.
-  ```select_related``` on ```ActivityLog.user``` 
- Don't call ```ActivityLog.arguments``` since fetches Addon objects, just dump ```_arguments``` to json and get the addon id.