Add an icon for the Stocks app.

Not great.  Better than nothing.

@hixie

examples/stocks/README.md

+## Icon
+
+Icon was created using Android Asset Studio:
+https://romannurik.github.io/AndroidAssetStudio/icons-launcher.html#foreground.type=image&foreground.space.trim=0&foreground.space.pad=0&foreColor=607d8b%2C0&crop=0&backgroundShape=square&backColor=fff%2C100&effects=none
+
+From this clipart:
+https://openclipart.org/detail/30403/tango-go-up
+Which is public domain.
+

examples/stocks/apk/AndroidManifest.xml

@@ -9,7 +9,7 @@
     <uses-sdk android:minSdkVersion="14" android:targetSdkVersion="21" />
     <uses-permission android:name="android.permission.INTERNET"/>
 
-    <application android:name="org.domokit.sky.shell.SkyApplication" android:label="Stocks">
+    <application android:icon="@mipmap/ic_launcher" android:name="org.domokit.sky.shell.SkyApplication" android:label="Stocks">
         <activity android:name="org.domokit.sky.shell.SkyActivity"
                   android:launchMode="singleTask"
                   android:theme="@android:style/Theme.Black.NoTitleBar"