Include source origin in string key name.

This should help eliminate string duplicates, as well as provide
visibility into where strings in a resource file are being used.

res/layout/recipients_panel.xml

@@ -16,7 +16,7 @@
             android:capitalize="sentences"
             android:autoText="true"
             android:singleLine="true"
-            android:hint="@string/to"
+            android:hint="@string/recipients_panel__to"
             android:paddingRight="45dip"
             android:textColor="#000000"
             android:layout_width="fill_parent"/>