CLC-1916 Rewrite semester feed to use Oracle

Revised version of #1124. Now, schedule and instructor data, which is section-specific, is cached at a global section level (instead of per-user) to gain some efficiency. Schedules and instructors are now arrays, which will break the front-end academics UI code. I've sent Scot a heads-up about this breakage. 

JIRA: https://jira.media.berkeley.edu/jira/browse/CLC-1916