LearnPress Co-instructor Add-on 4.0.4

~ Display on course offline
~ Optimize code
~ Use TomSelect instead of select2
~ User CourseModel instead of learn_press_get_course
~ Deprecated: before_admin_bar_course_item, restrict_co_instructor_items, get_available_courses, get_available_lessons, get_available_quizzes, get_available_questions, get_available_lesson_from_course, get_available_quizzes_from_course, get_available_question_from_quiz, co_instructor_valid_lessons, co_instructor_valid_quizzes, co_instructor_valid_questions
~ Remove template: single-course-tab.php

~ Tweak: field select co-instructor, get from API (make edit load screen edit courses faster)..