Styling tweaks to mitigate impact of bootstrap on top navbar.
Merge branch 'nalanda-rct2' into nalanda-rct3

Conflicts:
	kalite/student_testing/api_resources.py
	kalite/student_testing/models.py
	kalite/student_testing/utils.py
fixed width of playlist assign
IT IS DONE
all bugs fixed and Teach and Manage highlight when navigating subnavigation
Adding auth and first pass zone level csv export.
css bug fix on coach reports nav bar
cool hover effect on nav bar items!
Rework backbone code to 1) work and 2) disable options dynamically
Fix bug in resetting disabled attribute
Add FacilityUser endpoint
Add CSV serializer and endpoints for AttemptLog and testLog
Styling tweaks to reduce interference from Bootstrap.
Show link to store beside points as needed.
Tweaks for top nav, fixing spacing and duplicate IDs.
Fix to only drop non-current-unit exercise points when ds says so.
Fix to store view logic; avoid errors when purchased item not available.
Works for central server, added styles.
Embed store item images as data URIs.
Add "virtual" fields to FacilityUser resource