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/forum/src/components/ChangeEmailModal.js

@@ -0,0 +1,91 @@
+import Modal from 'flarum/components/Modal';
+
+/**
+ * The `ChangeEmailModal` component shows a modal dialog which allows the user
+ * to change their email address.
+ */
+export default class ChangeEmailModal extends Modal {
+  constructor(...args) {
+    super(...args);
+
+    /**
+     * Whether or not the email has been changed successfully.
+     *
+     * @type {Boolean}
+     */
+    this.success = false;
+
+    /**
+     * The value of the email input.
+     *
+     * @type {function}
+     */
+    this.email = m.prop(app.session.user.email());
+  }
+
+  className() {
+    return 'modal-sm change-email-modal';
+  }
+
+  title() {
+    return 'Change Email';
+  }
+
+  content() {
+    if (this.success) {
+      const emailProviderName = this.email().split('@')[1];
+
+      return (
+        <div className="modal-body">
+          <div class="form-centered">
+            <p class="help-text">We've sent a confirmation email to <strong>{this.email()}</strong>. If it doesn't arrive soon, check your spam folder.</p>
+            <div class="form-group">
+              <a href={'http://' + emailProviderName} className="btn btn-primary btn-block">Go to {emailProviderName}</a>
+            </div>
+          </div>
+        </div>
+      );
+    }
+
+    return (
+      <div className="modal-body">
+        <div class="form-centered">
+          <div class="form-group">
+            <input type="email" name="email" className="form-control"
+              placeholder={app.session.user.email()}
+              value={this.email()}
+              onchange={m.withAttr('value', this.email)}
+              disabled={this.loading}/>
+          </div>
+          <div class="form-group">
+            <button type="submit" className="btn btn-primary btn-block" disabled={this.loading}>Save Changes</button>
+          </div>
+        </div>
+      </div>
+    );
+  }
+
+  onsubmit(e) {
+    e.preventDefault();
+
+    // If the user hasn't actually entered a different email address, we don't
+    // need to do anything. Woot!
+    if (this.email() === app.session.user.email()) {
+      this.hide();
+      return;
+    }
+
+    this.loading = true;
+
+    app.session.user.save({email: this.email()}).then(
+      () => {
+        this.loading = false;
+        this.success = true;
+        m.redraw();
+      },
+      () => {
+        this.loading = false;
+      }
+    );
+  }
+}