Large refactor to remove classUid

[ryanhugh]

• Classes that were separated due to different titles (are therefore different classUids) are now combined
• honors was moved from the class object to the section object
  • Still need to add something to the frontend to show which sections are honors and which ones aren't
  • We could add like another column to the desktop class panel or something
  • All references to classUid were either removed or changed to classId
  • AddClassUids.js (and its tests) were deleted
  • prereqClassUids.js was renamed to markMissingClasses.js and most of the code was removed
  • Now all it does is mark missing prereqs and dosen't change any prereqs.
• Updated the docs

Going to merge this before the Facebook messenger PR!

Fixes #42