[FIX] mass_mailing: allow editing properly footer copyright

- ability to edit copyrights (change year, etc.) without removing ©
- 2016 in copyrights, not 2014

addons/mass_mailing/views/snippets_themes.xml

@@ -818,7 +818,7 @@
                     </tr>
                     <tr>
                         <td>
-                            <p class="o_mail_footer_copy">© 2014 All Rights Reserved</p>
+                            <p class="o_mail_footer_copy"><span class="fa fa-copyright"/> 2016 All Rights Reserved</p>
                         </td>
                     </tr>
                 </tbody>
@@ -841,7 +841,7 @@
                                 <a href="/unsubscribe_from_list" class="btn btn-link">Unsubscribe</a> | <a href="/page/contactus" class="btn btn-link">Contact</a>
                             </div>
                             <div>
-                                <p class="o_mail_footer_copy">© 2016 All Rights Reserved</p>
+                                <p class="o_mail_footer_copy"><span class="fa fa-copyright"/> 2016 All Rights Reserved</p>
                             </div>
                         </td>
                         <td t-if="website" class="o_mail_footer_social">