Improve playing a track with Google Earth

- directly send the play intent to Google Earth
- add a tour id to the feature to be played
- track the number of play using google analytics

SignalStrengthSamplerTest/AndroidManifest.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+      package="com.google.android.apps.mytracks.signalstrength.test"
+      android:versionCode="1"
+      android:versionName="1.0">
+  <application android:label="Signal Strenght Sampler Test">
+    <uses-library android:name="android.test.runner" />
+  </application>
+  <uses-sdk android:minSdkVersion="7" />
+  <instrumentation android:targetPackage="com.google.android.apps.mytracks.signalstrength"
+                   android:name="android.test.InstrumentationTestRunner" />
+</manifest>