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/admin/src/components/SettingsModal.js

@@ -39,7 +39,7 @@ export default class SettingsModal extends Modal {
   }
 
   setting(key, fallback = '') {
-    this.settings[key] = this.settings[key] || m.prop(app.settings[key] || fallback);
+    this.settings[key] = this.settings[key] || m.prop(app.data.settings[key] || fallback);
 
     return this.settings[key];
   }
@@ -50,7 +50,7 @@ export default class SettingsModal extends Modal {
     Object.keys(this.settings).forEach(key => {
       const value = this.settings[key]();
 
-      if (value !== app.settings[key]) {
+      if (value !== app.data.settings[key]) {
         dirty[key] = value;
       }
     });