Massive JavaScript cleanup

- Use JSX for templates
- Docblock/comment everything
- Mostly passes ESLint (still some work to do)
- Lots of renaming, refactoring, etc.

CSS hasn't been updated yet.

js/lib/helpers/listItems.js

@@ -0,0 +1,37 @@
+import Separator from 'flarum/components/Separator';
+
+function isSeparator(item) {
+  return item && item.component === Separator;
+}
+
+function withoutUnnecessarySeparators(items) {
+  const newItems = [];
+  let prevItem;
+
+  items.forEach((item, i) => {
+    if (!isSeparator(item) || (prevItem && !isSeparator(prevItem) && i !== items.length - 1)) {
+      prevItem = item;
+      newItems.push(item);
+    }
+  });
+
+  return newItems;
+}
+
+/**
+ * The `listItems` helper wraps a collection of components in <li> tags,
+ * stripping out any unnecessary `Separator` components.
+ *
+ * @param {Array} items
+ * @return {Array}
+ */
+export default function listItems(items) {
+  return withoutUnnecessarySeparators(items).map(item => {
+    const isListItem = item.component && item.component.isListItem;
+    const className = item.props ? item.props.itemClassName : item.itemClassName;
+
+    return isListItem
+      ? item
+      : <li className={(item.itemName ? 'item-' + item.itemName : '') + ' ' + (className || '')}>{item}</li>;
+  });
+};