Summary metrics table

[dgershman]

a breakout of which area got how many calls for volunteer calls would be a huge help to regions/zones for reporting, so we don't hve to pull separately for 20 areas or whatever.

[dgershman]

The database work for this is trivial. The complexity is really around making changes to the display. I probably will wait until we redo things in React. Here are the API/DB changes.

https://github.com/bmlt-enabled/yap/tree/feature/metrics-grouped