Add storage library (and demo app)

and use for periodic files backup
diff --git a/app/src/main/AndroidManifest.xml b/app/src/main/AndroidManifest.xml
index 2fc78cf..7b8504f 100644
--- a/app/src/main/AndroidManifest.xml
+++ b/app/src/main/AndroidManifest.xml
@@ -113,5 +113,18 @@
             </intent-filter>
         </receiver>
 
+        <!-- Used to start actual BackupService depending on scheduling criteria -->
+        <service
+            android:name=".storage.StorageBackupJobService"
+            android:exported="false"
+            android:label="BackupJobService"
+            android:permission="android.permission.BIND_JOB_SERVICE" />
+        <!-- Does the actual backup work as a foreground service -->
+        <service
+            android:name=".storage.StorageBackupService"
+            android:exported="false"
+            android:foregroundServiceType="dataSync"
+            android:label="BackupService" />
+
     </application>
 </manifest>