Updated Course ID Regex and CSV filename

This regex is nearly identical to the one used by LMS. The only difference is the internal capture groups have been replaced with character sets to avoid issues with the Swagger UI attempting to parse the internal capture groups and pass them along as arguments.

@rocha @dsjen @mulby @brianhw 
Can you add a test that uses a valid unicode character in the new-format course-id?  It would be good to know sooner rather than later that we handle this case.