[bug 920166] Add product pickers to metric dashboards.

To verify: 

* Run tests.
* Go to aggregated L10n dashboard (/en-US/kb/dashboard/metrics/aggregated) and verify the product picker is there and does something.
* Go to a locale metrics dashboard (/en-US/kb/dashboard/metrics/es for Spanish, for example) and verify the product picker is there and does something.
* Go to the questions metrics dashboard (/en-US/questions/dashboard/metrics) and verify the product picker is there and does something.

r?