[ZEPPELIN-3491][Minor] Add apple-touch-icon.png to Zeppelin project

This JIRA is to add apple-touch-icon.png to Zeppelin project

[Minor]

* [ZEPPELIN-3491](https://issues.apache.org/jira/browse/ZEPPELIN-3491)

* Does the licenses files need update? N/A
* Is there breaking changes for older versions? N/A
* Does this needs documentation? N/A

Author: Prabhjyot Singh <prabhjyotsingh@gmail.com>

Closes #2981 from prabhjyotsingh/ZEPPELIN-3491 and squashes the following commits:

d55a73f [Prabhjyot Singh] [ZEPPELIN-3491] Add apple-touch-icon.png to Zeppelin project

Change-Id: I16f8aa1cdcc0f33fcc0f728a55155ac2b1b401f6

zeppelin-web/src/index.html

@@ -33,7 +33,8 @@
        div.ace_editor.ace_autocomplete .ace_marker-layer .ace_active-line { z-index: -1 !important; }
     </style>
 
-    <!-- Place favicon.ico and apple-touch-icon.png in the root directory -->
+    <link rel="apple-touch-icon" href="apple-touch-icon.png" />
+    <link rel="icon" type="image/x-icon" href="favicon.ico" />
     <!-- build:css(.) styles/vendor.css -->
     <!-- bower:css -->
     <link rel="stylesheet" href="bower_components/bootstrap/dist/css/bootstrap.css" />