REFACTOR: replace low level access to Role table with rolify api calls`

[pconrad]

Look for code such as:

    Role.where(name: "instructor", resource_id: self.id).first.users.first

And consider whether each line of code that accesses the Role table might be better implemented with a call to an api method of the rolify gem.

Acceptance Criteria

• [ ] Wnen you do a global search on Role. you do not find any direct access to the Role table, unless it is commented with a specific justification for why we are doing it that way instead of going through the rolify api.