MDL-47058 core_grades: removed unnecessary print_object call

Part of MDL-46576.
MDL-47058 core_grades: allow alteration of weight

Part of MDL-46576
MDL-47055 core_grade: implemented support for extra credit within natural weighting
MDL-47007 core_grade: weights now shown on edit screen as percentages
MDL-46827 usability: New icon for reset actions
MDL-46827 core_grades: Allow reset of weights on categories
MDL-47055 core_grade: fixed extra credit handling on the full setup page
MDL-47098 core_grades: Fields to adjust a category's weight