add family_name and version_year to courses

[davidsbailey]

This PR accomplishes a few cleanup steps related to course versioning:

1. adds family_name and version_year fields as course properties
2. reads new field values explicitly rather than inferring them from the course name
3. starts using family_name explicitly when selecting courses from the db
4. adds a new test for /courses/csd --> csd-2018 redirection logic, but doesn't change that logic to use db values yet. that work will likely involve adding a new "course family cache"

[balderdash]

Looks great!

[davidsbailey]

Excellent, thanks for the ongoing reviews!