Compute points only on login, or when points change.
Fixing import bug, reducing queries for teachers.
use cached session to avoid (slow) db-writes when updating session data
Merge branch 'develop' of github.com:learningequality/ka-lite into cache_total_points

Conflicts:
	kalite/main/api_views.py
fixing RPi redirect at login and merge conflict marker leftover
Merge branch 'develop' of github.com:learningequality/ka-lite into cache_total_points

Conflicts:
	kalite/main/api_views.py
	kalite/static/js/search_autocomplete.js
Merge pull request #819 from bcipolli/cache_total_points

Cache total points