Added a help link to the Analytics UI

The analytics service shows an option to the user to asking them to
"enable advertising ID" - there's now an additional link a user can
click to read more.

Change-Id: I8ebff94980854e5b891897313db2a5fa6db2a24f
diff --git a/resources/analytics/service.xml b/resources/analytics/service.xml
index cc9b885..97f0ddb 100644
--- a/resources/analytics/service.xml
+++ b/resources/analytics/service.xml
@@ -77,8 +77,17 @@
         text="${google.analytics.propertyId}"/>
   </uiGrid>
 
-  <uiItem
-    type="checkbox"
-    text="Enable Advertising ID"
-    checked="${google.analytics.adsEnabled}"/>
+  <uiGrid colDefinitions="100px,Fit,Fit">
+    <uiItem
+      col="1"
+      type="checkbox"
+      text="Enable Advertising ID"
+      checked="${google.analytics.adsEnabled}"/>
+
+    <uiItem
+      col="2"
+      type="link"
+      text="What's this?"
+      url="https://developers.google.com/analytics/devguides/collection/android/v4/#ad-id"/>
+  </uiGrid>
 </service>