Update copyright year in few places

index.php

@@ -4,7 +4,7 @@
  | Roundcube Webmail IMAP Client                                           |
  | Version 1.4-git                                                         |
  |                                                                         |
- | Copyright (C) 2005-2017, The Roundcube Dev Team                         |
+ | Copyright (C) 2005-2018, The Roundcube Dev Team                         |
  |                                                                         |
  | This program is free software: you can redistribute it and/or modify    |
  | it under the terms of the GNU General Public License (with exceptions   |

skins/classic/templates/about.html

@@ -20,7 +20,7 @@
 <div id="license">
 <roundcube:object name="aboutcontent" />
 <h2 class="sysname">Roundcube Webmail <roundcube:object name="version" /></h2>
-<p class="copyright">Copyright &copy; 2005-2017, The Roundcube Dev Team</p>
+<p class="copyright">Copyright &copy; 2005-2018, The Roundcube Dev Team</p>
 <p class="license">This program is free software; you can redistribute it and/or modify
 it under the terms of the <a href="http://www.gnu.org/licenses/gpl.html" target="_blank">GNU General Public License</a>
 as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.<br/>

skins/elastic/templates/about.html

@@ -6,7 +6,7 @@
 
 <div class="content frame-content">
 	<h2 class="sysname">Roundcube Webmail <roundcube:object name="version" /></h2>
-	<p class="copyright">Copyright &copy; 2005-2016, The Roundcube Dev Team</p>
+	<p class="copyright">Copyright &copy; 2005-2018, The Roundcube Dev Team</p>
 	<p class="license">This program is free software;
 		you can redistribute it and/or modify it under the terms of the 
 		<a href="http://www.gnu.org/licenses/gpl.html" target="_blank">GNU General Public License</a>

skins/larry/templates/about.html

@@ -10,7 +10,7 @@
 <roundcube:object name="aboutcontent" />
 
 <h2 class="sysname">Roundcube Webmail <roundcube:object name="version" /></h2>
-<p class="copyright">Copyright &copy; 2005-2017, The Roundcube Dev Team</p>
+<p class="copyright">Copyright &copy; 2005-2018, The Roundcube Dev Team</p>
 <p class="license">This program is free software; you can redistribute it and/or modify
 it under the terms of the <a href="http://www.gnu.org/licenses/gpl.html" target="_blank">GNU General Public License</a>
 as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.<br/>