add the powerpoint button on the left-nav-bar

OfficeJS/component/left_nav_bar.html

@@ -44,6 +44,15 @@
       New Spreadsheet
     </a>
   </li>
+  <li class="spreadsheet left-nav-tools">
+    <a href="#/powerpoint"
+       onclick="javascript:
+                OfficeJS.open({app:'powerpoint'});
+                return false;">
+      <i class="icon-facetime-video"></i>
+      New Powerpoint
+    </a>
+  </li>
   <!-- <li class="editpreferences left-nav-tools"> -->
   <!--   <a href="#/edit_preferences" -->
   <!--      onclick="javascript: -->