WIP: Documentation for Publishing Changes

Seems like users can get unit and component confused, so might be helpful to say a unit can include one component (for example, a video) or more than one (a video, and a multiple choice question) and show a screen shot of each. We should also point out that if course staff want to hide graded assignments after the course ends (link to course closing options), it's easier if there is one component per unit. This is complicated, but 4.605 learned the hard way when they went to archive the course and realized that they had multiple components per unit and could only hide at the unit level. Not sure if this is still the case with the new changes, but something to think about. Common practice in archived courses is to leave video up and hide assessments.