Refactor the web app bootstrapping code

- All custom JS variables are now preloaded into the `app.data` object, rather than directly on the `app` object. This means that admin settings are available in `app.data.settings` rather than `app.settings`, etc.
- Cleaner route handler generation
- Renamed ConfigureClientView to ConfigureWebApp, though the former still exists and is deprecated
- Partial fix for #881 (strips ?nojs=1 from URL if possible, so that refreshing will attempt to load JS version again)

js/forum/src/components/HeaderSecondary.js

@@ -39,14 +39,14 @@ export default class HeaderSecondary extends Component {
 
     items.add('search', app.search.render(), 30);
 
-    if (Object.keys(app.locales).length > 1) {
+    if (Object.keys(app.data.locales).length > 1) {
       const locales = [];
 
-      for (const locale in app.locales) {
+      for (const locale in app.data.locales) {
         locales.push(Button.component({
-          active: app.locale === locale,
-          children: app.locales[locale],
-          icon: app.locale === locale ? 'check' : true,
+          active: app.data.locale === locale,
+          children: app.data.locales[locale],
+          icon: app.data.locale === locale ? 'check' : true,
           onclick: () => {
             if (app.session.user) {
               app.session.user.savePreferences({locale}).then(() => window.location.reload());