doxy: fix sparkfun image license version in template

Sparkfun provided images are covered under CC BY 2.0, update license on documentation template to reflect correct license.

Signed-off-by: Mihai Tudor Panu <[email protected]>

Author: Propanu

doxy/node/generators/yuidoc/tmpl/layouts/main.handlebars

@@ -18,7 +18,7 @@
           <p>
           The UPM API is a high level sensor library for IoT devices using MRAA. See examples <a href="https://github.com/intel-iot-devkit/upm/tree/master/examples/javascript">here</a>. 
           Back to <a href="http://iotdk.intel.com/docs/master/upm/node/"> index </a> page.
-          <br><em>SparkFun sensor images provided under <a href=https://creativecommons.org/licenses/by-nc-sa/3.0/>CC BY-NC-SA-3.0</a>.</em>
+          <br><em>SparkFun sensor images provided under <a href=https://creativecommons.org/licenses/by/2.0/>CC BY 2.0</a>.</em>
           </p>
         </div>
     </div>