Control panel & fix for summary stats not showing

Ok, this addresses https://github.com/fle-internal/ka-lite-central/issues/151 AND https://github.com/learningequality/ka-lite/issues/2129

Previous PR https://github.com/learningequality/ka-lite/pull/2128 had a small bug that I found during these changes and have fixed here as well. 

Major changes:
* summary stats now show correctly for group views
* we are using bootstrap now selectively on control panel pages which means nicer looking tables, using glypicons, and select boxes for selecting and deselecting rows. 

The front end code will be overwhelming to code review, I suggest focusing on two main files:

@aronasorman if you could briefly peak at my changes to control_panel/views -- this is where the bug has been fixed re: summary stats and is the only backend side of things I touched

@rtibbles if you could test out the views and take a look at facility_management.js to see my changes to your JS that would be awesome. I wasn't able to hook up the select and drag on top of the checkboxes, but left the code and the hooks there in the hope it would be simple for you to do or show me how before we merge this. 

Some screenshots:

![image](https://cloud.githubusercontent.com/assets/1319950/3136430/59137770-e842-11e3-9986-096417e93cca.png)
New overview page

![image](https://cloud.githubusercontent.com/assets/1319950/3136442/7bb0fdf2-e842-11e3-88b6-71f1ff2154b1.png)
Top of new zone page 

![image](https://cloud.githubusercontent.com/assets/1319950/3136434/6c6b5d1a-e842-11e3-8473-e5215837cffc.png)
scrolled part of the new Zone page 

![image](https://cloud.githubusercontent.com/assets/1319950/3136452/92d34b3e-e842-11e3-9b44-e91eb5b7c7a1.png)
Group info page with summary stats working (for the student group "Mike Wray" in honor of our most dedicated tester! @mikewray