ui: Initial Elm UI import

Merged from https://github.com/jhillyerd/inbucket-elm

Uses https://github.com/halfzebra/create-elm-app

ui/src/index.js

@@ -0,0 +1,33 @@
+import './main.css';
+import { Main } from './Main.elm';
+import registerServiceWorker from './registerServiceWorker';
+
+var app = Main.embed(document.getElementById('root'), sessionObject());
+
+app.ports.storeSession.subscribe(function (session) {
+  localStorage.session = JSON.stringify(session);
+});
+
+app.ports.windowTitle.subscribe(function (title) {
+  document.title = title;
+});
+
+window.addEventListener("storage", function (event) {
+  if (event.storageArea === localStorage && event.key === "session") {
+    app.ports.onSessionChange.send(sessionObject());
+  }
+}, false);
+
+function sessionObject() {
+  var s = localStorage.session;
+  try {
+    if (s) {
+      return JSON.parse(s);
+    }
+  } catch (error) {
+    console.error(error);
+  }
+  return null;
+}
+
+registerServiceWorker();