Make the course URL pattern more generic.

Comment newly added functionality.

Fix quality issues.

Address two lint errors, with regex and variable naming.

Changed how we access course_key and course_id.

Replace another instance of self.course.id.to_deprecated_string()

Remove unused import, add missing one.

Improve how the ccx key is extracted from the URL

Use resolve() instead of os.path to get the course_id.

Remove the granting of staff access to coaches.