Editor: Add suggested course

[Will Ceolin]

On the lesson step, allow to add a suggested course. It allows to add only courses from the current school for now.

Tasks

Beta Give feedback

1. Add schema
2. Create suggested course
3. Delete suggested course
4. List suggested courses
5. Search courses by title, slug
6. Editor: Button to add suggested course (opens search box)
7. Search box: Clicking on the result adds course
8. Editor: List suggested courses
9. Editor: Remove suggested course
10. Adds tests for controller
11. Update locale