Add ability to prefetch and auto-prefetch offline data

src/app/components/option-picker/option-picker.component.html

@@ -11,6 +11,14 @@
     <i slot="start" class="fa" [ngClass]="isDark() ? 'fa-sun' : 'fa-moon'"></i>
     <ion-label>{{ isDark() ? 'To The Light!' : 'Go Dark...' }}</ion-label>
   </ion-item>
+  <ion-item button (click)="onSelect('prefetch_data')">
+    <i slot="start" class="fa fa-download"></i>
+    <ion-label>Prefetch Offline Data</ion-label>
+  </ion-item>
+  <ion-item button (click)="onSelect('toggle_auto_prefetch')">
+    <i slot="start" class="fa" [ngClass]="isPrefetch() ? 'fa-check-square' : 'fa-square'"></i>
+    <ion-label>Auto-Prefetch</ion-label>
+  </ion-item>
   <ion-item button (click)="onSelect('logout')">
     <i slot="start" class="fa fa-sign-out-alt"></i>
     <ion-label>Logout</ion-label>