Integrate embed templates into detail view.
Replace progress bar with macro throughout generator.
Hook up banner list in dashboard.
Bug 993237: Add aggregation command and overwrite old stats upon update.

- Adds a command for aggregating clicks and downloads that are older 
  than 90 days.
- Updates the collect_ga_data command to accept a date argument for
  easier testing, and to overwrite existing stats instead of raising
  an error due to unique constraints.