* schoolutils/grading/ui.py: edit_table: print empty line for clarity
* schoolutils/grading/ui.py: edit_student_courses: avoid prompting user if no available courses to add
* schoolutils/grading/ui.py: enter_grades: various UI improvements
  - offer to add student to course if not a member
  - better printing of existing grades
  - use name-based col access
* docs/project.org: TODO updates