Switch to a simpler storage model.

Going back to the previous storage model of where we only store the messages.
We reference records by appending the offset of the record to the end of the
uri.

When a tag is discovered we start the service to save it. A PendingIntent
is created that will resolve to the currently running activity.

Change-Id: I32d1dd70960fdf67129d1707399d667de030ebe5
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index 280ad6f..d12185b 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -47,6 +47,7 @@
 
         <activity android:name="TagViewer"
             android:theme="@android:style/Theme.NoTitleBar"
+            android:launchMode="singleTop"
         >
             <intent-filter>
                 <action android:name="android.nfc.action.NDEF_TAG_DISCOVERED"/>
@@ -68,7 +69,6 @@
             android:authorities="com.android.apps.tag"
             android:syncable="false"
             android:multiprocess="false"
-            android:exported="false"
         />
 
     </application>