learningequality/ka-lite — pull request #628 by bcipolli (2013-09-03 04:52:45+00:00)
Title: removing the static, disk-based node cache.

We don't need it. This can be built dynamically with really little overhead--a single traversal through the topic tree. In fact, this is the amount of work needed to build the "moviecounts"--which we've already seen no problems from.

This:
* Saves disk space
* Avoids duplicating topic data on disk (making our migration to Phase 2 easier).

This change also adds a "parents" list to NODE_CACHE, for efficient association of an exercise/video/topic with parent topics.