Updates the copyright to 2021 for all files that have a copyright. Files in our source code without the copyright header still do not receive one automatically. Additionally, backlisted files are also excluded.
Previously the copyright of chiliproject which references redmine stated a copyright of redmine up to and including 2017 which is not true for the code we have in here. Because of that I changed that to 2013
* renders a partial without the mentioned elements
* when using standard request the information is still presented. This enables opening the diff in a new tab/window.