C2: Check if one gradebook is created on course creation

[ywarnier]

In Chamilo 1, the gradebook's main record is only created on first load of a teacher in the gradebook tool. This was a patch.

Make sure the gradebook is created on course creation in C2.

[ywarnier]

The entry in gradebook_category is still only created on tool visit by a teacher.
This should be created upon course creation.

[ywarnier]

This is developing into something much larger, where I will go through the removal of all references to course_code in the gradebook libraries (in favor of course ID (ci_id) which has already been the new foreign key for a while in C2).

[ywarnier]

The code to create the first gradebook in a course is in public/main/gradebook/index.php line ~764