MAGETWO-86452: [Backport for 2.2.x] Update copyright year

COPYING.txt

-Copyright © 2013-2018 Magento, Inc.
+Copyright © 2013-present Magento, Inc.
 
 Each Magento source file included in this distribution is licensed under OSL 3.0 or the Magento Enterprise Edition (MEE) license
 

app/code/Magento/Theme/etc/config.xml

@@ -45,7 +45,7 @@ Disallow: /*SID=
                 <welcome>Default welcome msg!</welcome>
             </header>
             <footer translate="copyright">
-                <copyright>Copyright &#169; 2013-2018 Magento, Inc. All rights reserved.</copyright>
+                <copyright>Copyright &#169; 2013-present Magento, Inc. All rights reserved.</copyright>
             </footer>
         </design>
         <theme>

app/code/Magento/Theme/i18n/en_US.csv

@@ -142,7 +142,7 @@ Empty,Empty
 "1 column","1 column"
 Configuration,Configuration
 "Default welcome msg!","Default welcome msg!"
-"Copyright © 2013-2018 Magento, Inc. All rights reserved.","Copyright © 2013-2018 Magento, Inc. All rights reserved."
+"Copyright © 2013-present Magento, Inc. All rights reserved.","Copyright © 2013-present Magento, Inc. All rights reserved."
 "Design Config Grid","Design Config Grid"
 "Rebuild design config grid index","Rebuild design config grid index"
 "Admin empty","Admin empty"

dev/tests/integration/testsuite/Magento/Theme/Controller/Adminhtml/System/Design/Config/SaveTest.php

@@ -67,7 +67,7 @@ class SaveTest extends AbstractBackendController
             'header_logo_height' => '',
             'header_logo_alt' => '',
             'header_welcome' => 'Default welcome msg!',
-            'footer_copyright' => 'Copyright © 2013-2018 Magento, Inc. All rights reserved.',
+            'footer_copyright' => 'Copyright © 2013-present Magento, Inc. All rights reserved.',
             'footer_absolute_footer' => '',
             'default_robots' => 'INDEX,FOLLOW',
             'custom_instructions' => '',