Explicitly define backup rules

* So that we don't go over the backup limit (25MB) by including
  APKs and the local swap repo in the backup

app/src/main/AndroidManifest.xml

@@ -64,7 +64,7 @@
             android:label="@string/app_name"
             android:description="@string/app_description"
             android:allowBackup="true"
-            android:fullBackupContent="true"
+            android:fullBackupContent="@xml/backup_rules"
             android:theme="@style/AppThemeLight"
             android:supportsRtl="true">
 

app/src/main/res/xml/backup_rules.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<full-backup-content>
+	<!-- Don't include apks or the local swap repo -->
+    <exclude domain="file" path="."/>
+</full-backup-content>