Adds an option and hide avatars in contact list.

interface_config.js

     // screen, 'width' would fit the original video width to the width of the
     // screen respecting ratio.
     VIDEO_LAYOUT_FIT: 'both',
+    SHOW_CONTACTLIST_AVATARS: false,
     /**
      * Whether to only show the filmstrip (and hide the toolbar).
      */

modules/UI/side_pannels/contactlist/ContactList.js

-/* global $, APP */
+/* global $, APP, interfaceConfig */
 import Avatar from '../../avatar/Avatar';
 import UIEvents from '../../../../service/UI/UIEvents';
 import UIUtil from '../../util/UIUtil';
             }
         };
 
-        newContact.appendChild(createAvatar(id));
+        if (interfaceConfig.SHOW_CONTACTLIST_AVATARS)
+            newContact.appendChild(createAvatar(id));
         newContact.appendChild(createDisplayNameParagraph("participant"));
 
         if (APP.conference.isLocalId(id)) {