Course repository example

A complete, valid course in the "one course, one repository" layout: course.yaml at the root, units/ beside it, IDs relative to the course (u01, u01/l01). It also carries the optional frameworks/ and school/ folders, so the validator checks every sci:... and eso:... reference against them. Copy this folder to start a new course.

Goals align to framework items (sci:...) or to goals inside the course (u01#goal1). A reference to a framework prefix the course does not carry is accepted; one under a carried prefix must exist.