Add translation support

Change-Id: I8cc38cd00683ce6f0ef8f62eb9eeddfc84c52a34

src/App.js

@@ -1,9 +1,22 @@
 import React from "react";
-import { Admin, Resource } from "react-admin";
+import { Admin, Resource, resolveBrowserLocale } from "react-admin";
+import polyglotI18nProvider from "ra-i18n-polyglot";
 import dataProvider from "./dataProvider";
+import germanMessages from "./i18n/de";
+import englishMessages from "./i18n/en";
+
+// TODO: Can we use lazy loading together with browser locale?
+const messages = {
+  de: germanMessages,
+  en: englishMessages,
+};
+const i18nProvider = polyglotI18nProvider(
+  locale => (messages[locale] ? messages[locale] : messages.en),
+  resolveBrowserLocale()
+);
 
 const App = () => (
-  <Admin dataProvider={dataProvider}>
+  <Admin dataProvider={dataProvider} i18nProvider={i18nProvider}>
     <Resource name="data" />
   </Admin>
 );

src/i18n/de.js

@@ -0,0 +1,5 @@
+import germanMessages from "ra-language-german";
+
+export default {
+  ...germanMessages,
+};

src/i18n/en.js

@@ -0,0 +1,5 @@
+import englishMessages from "ra-language-english";
+
+export default {
+  ...englishMessages,
+};