Add Course, Subject, and CourseTags models
Add models for CoreData entities
Remove unneeded attributes from tags
Fix inconsistencies with inverse relationships
Setup "LoadedData" model that keeps track of course versions
Remove LoadedData date. We can just sort by version.
Add sekelton code to load seed courses from local/remote
Handle checking for new versions for updating course data

This will initalize the various course related models from a local
CourseSeed plist if we have no versions.

Also check if the remote CourseSeed is a newer version that we can
update from