content database too complicated, should be flat

[qdonnellan]

Need to change the content database to be more flat (don't need the crazy "lessons have unit parents have course parents") instead, lessons should have a unit attribute that points to the id in the same database model

[qdonnellan]

working on implementing a new solution such that all Curriculum contents only have two attributes, for example

Curriculum(
    content_type = 'course', 
    content = {
        teacher : 1234,
        private : False,
        approved_students : [123, 456],
    }