Automatized changes to license and copyright information

These are automatically created changes. They should include

• a LICENSE.txt file, if such a file was not already present
• added copyright headers to all .py, .scala files that did not already had one
• updated copyright headers to all .py, .scala files that attribute copyright to the non existing legal entity NOMAD Developers Group

Please do carefully check the proposed changes and accept the merge if appropriate, or comment to this merge request otherwise.