Finish admin permissions page and clean up everything

js/admin/src/components/ConfigDropdown.js

@@ -0,0 +1,25 @@
+import SelectDropdown from 'flarum/components/SelectDropdown';
+import Button from 'flarum/components/Button';
+import saveConfig from 'flarum/utils/saveConfig';
+
+export default class ConfigDropdown extends SelectDropdown {
+  static initProps(props) {
+    super.initProps(props);
+
+    props.className = 'ConfigDropdown';
+    props.buttonClassName = 'Button Button--text';
+    props.caretIcon = 'caret-down';
+    props.defaultLabel = 'Custom';
+
+    props.children = props.options.map(({value, label}) => {
+      const active = app.config[props.key] === value;
+
+      return Button.component({
+        children: label,
+        icon: active ? 'check' : true,
+        onclick: saveConfig.bind(this, {[props.key]: value}),
+        active
+      });
+    });
+  }
+}