OmniControl: Add sharedUserId `android.uid.system` to AndroidManifest.xml

It's allowed to store data with android UID for battery settings with our new SDK frameworks

Fix:
E AndroidRuntime: FATAL EXCEPTION: main
E AndroidRuntime: Process: org.omnirom.control, PID: 4762
E AndroidRuntime: java.lang.SecurityException: Given calling package android does not match caller's uid 10121

Change-Id: Ia282321484ebd1bd7dc0c14cb81069dceef101ca
diff --git a/app/src/main/AndroidManifest.xml b/app/src/main/AndroidManifest.xml
index 0ea1f8d..1d83391 100644
--- a/app/src/main/AndroidManifest.xml
+++ b/app/src/main/AndroidManifest.xml
@@ -3,7 +3,8 @@
     xmlns:tools="http://schemas.android.com/tools"
     package="org.omnirom.control"
     android:versionCode="1"
-    android:versionName="1.0">
+    android:versionName="1.0"
+    android:sharedUserId="android.uid.system">
 
     <uses-permission
         android:name="android.permission.WRITE_SETTINGS"