Fixes #853

Update

• questionModel.js — added @file/@module header, @class block, and JSDoc for all public methods (canSubmit, isCorrect, isPartlyCorrect, getFeedback, isInteractive, reset, resetQuestion, refresh, getButtonState, getInteractionObject, getResponse, getResponseType, onSubmitted, addContextActivity, addContentObjectContextActivities, contextActivities, score, maxScore, minScore, setScore); removed 13 redundant inline comments that restated method names
• itemModel.js — added @file/@module header, @class block, and JSDoc for toggleClass, toggleActive, and toggleVisited; fixed pre-existing @param name {type} tag order to standard @param {type} name
• itemsComponentModel.js — added @file/@module header, @class block, and JSDoc for restoreUserAnswers, storeUserAnswer, getItem, and setActiveItem
• itemsQuestionModel.js — added @file/@module header, @class block, and JSDoc for restoreUserAnswers, setupRandomisation, storeUserAnswer, isCorrect, getFeedback, score, maxScore, minScore, getInteractionObject, getResponse, getResponseType, getCorrectAnswerAsText, and getUserAnswerAsText; fixed two malformed /**\n * JSDoc blocks

Testing

1. Run grunt build and verify no JS errors
2. Open a course with an MCQ component; confirm question submits, marks, and resets correctly