Add subscription_totals widget to the dashboard.

These changes add the markup, styles, routes, and look like many other
existing widgets in our code. The code in these changes reflect the
initial, rudimentary subscription_totals widget.
Remove dropbutton for quantity from subscriptions totals widget.
Add tests for active and expiring soon subscriptions.
Add test for recently expired subscription totals.
Update subscription_totals widget queries

These changes include updating the links on the dashboard to query
elasticsearch using date ranges to find recently-expired as well as
soon-to-expire subscriptions.