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
When running in production
* product_version will be set on SaaS
* product_version will be nil but caches are cleared when running package based
When running in development production version will also be nil but VERSION will include the git sha
Ivan Kuchin