better manage discourse features

Larry Craig

People who use this feature are probably people who have taken Morris Proctor courses. He says that these features are in 5 categories. We should have the ability if not to select or deselect all features at once, we should at least then be able to select or deselect the categories all at once. It's too tedious now. In fact, group the features according to these 5 categories rather than having one very long list to work with.