PLT-5860 Updated copyright date (#6058)

* PLT-5860 Updated copyright date in about modal

* PLT-5860 Updated copyright notice in JSX files

* PLT-5860 Updated copyright notice in go files

* Fixed misc copyright dates

* Fixed component snapshots

webapp/tests/components/__snapshots__/about_build_modal.test.jsx.snap

@@ -127,9 +127,13 @@ exports[`components/AboutBuildModal should match snapshot for enterprise edition
         className="form-group about-modal__copyright"
       >
         <FormattedMessage
-          defaultMessage="Copyright 2016 Mattermost, Inc. All rights reserved"
+          defaultMessage="Copyright 2015 - {currentYear} Mattermost, Inc. All rights reserved"
           id="about.copyright"
-          values={Object {}}
+          values={
+            Object {
+              "currentYear": 2017,
+            }
+          }
         />
       </div>
     </div>
@@ -294,9 +298,13 @@ exports[`components/AboutBuildModal should match snapshot for team edition 1`] =
         className="form-group about-modal__copyright"
       >
         <FormattedMessage
-          defaultMessage="Copyright 2016 Mattermost, Inc. All rights reserved"
+          defaultMessage="Copyright 2015 - {currentYear} Mattermost, Inc. All rights reserved"
           id="about.copyright"
-          values={Object {}}
+          values={
+            Object {
+              "currentYear": 2017,
+            }
+          }
         />
       </div>
     </div>