Add copyright headers

Dear @jordiarjona ,

We analysed the current code and found that copyright headers were missing from the majority of the source code files. We have produced a 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 "Instituto Tecnologico de Informatica (ITI)". I have had to remove the accents as the tool was not running with them; I'm sorry for this. If you still want them, you can add them manually in each header. You could use this Merge Request issue for this.

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 @pkriefrvi @asgomes