Analytics DB: Set up materialized views for dashboard queries

[jjnesbitt]

The queries we make for the grafana dashboards can be quite heavy, and without any caching, are executed far more often than is necessary. Simply loading the page sends all of the necessary queries, along with refreshing every x seconds.

We should create materialized views for these queries. We could store them in a new dashboard schema, and use un-managed Django models, along with celery cron tasks, to periodically refresh these views.