Basic framework for browser-based views for sensor/prediction graphs
Change default top_level_container_name for itsisu to be "activity" (as it is on pro)

In config/initializers/01_load_config.rb on line 25 we try to set the class for the top-level container.( http://bit.ly/1jRCAK6 )

The default configuration for itsi sets the TOP_LEVEL_CONTAINER_NAME to "Unit" -- but ::Unit is not an actual class name, so I keep getting `uninitialized constant Unit`

On production this is set to "Activity".
[#74884614] Activate the grade_level, subject_area, and unit drop-downs for teachers

There was concern that this might cause non-exemplars to show up in the activity bins. They won't, because
the re-binning happens by overriding the grade-level and subject areas for the view if the activity is not an exemplar.

https://www.pivotaltracker.com/story/show/74884614