Add copyright headers

Dear @bjaniak ,

We analysed the current code and found that copyright headers were missing in the source code files. We have produced this Merge Request to show mainly the type of headers we expect when IP Reviewing open source code.

We invite you to check each change because there are some cases in which the addition of the header can create issues, like in files which are input for another process and we are not sure if comments or a header are expected. Please have a look at them.

You'll notice we've assigned ownership to "Poznan Supercomputing and Networking Center (PSNC)", as you indicated by email.

You will notice as well that in each file there is a placeholder for the Contributors (last section in the header). Feel free to add your name and contribution, or other's names there.

Feel free to be inspired and/or accept the whole Merge Request.

Thanks a lot

/cc @asgomes