Add some copyright headers

Dear @urtain ,

We analysed the current code and found that you have already added the copyright headers to most of the files, well done. We have produced this Merge Request to add the headers to a few files where the copyright header was missing.

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.

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

Thanks for helping adding the headers yourself.

/cc @asgomes