feat navigation: style checkboxes in navigation

feat preferences: Show Hidden Files and Show Directories First options working

src/js/actions/settings.js

@@ -0,0 +1,8 @@
+import { SETTINGS } from 'actions/types';
+
+export default function(props) {
+  return {
+    type: SETTINGS,
+    ...props
+  }
+}

src/js/actions/types.js

@@ -20,6 +20,8 @@ const TYPES = {
 
   DIALOG: Symbol('DEBUG'),
 
+  SETTINGS: Symbol('SETTINGS'),
+
   SEARCH: Symbol('SEARCH')
 };