small restructuring of header generation

This is just a small restructure of the way the header gets generated.
This should soon allow for updates to the po file.

moment is used to format the date (and possibly parse in the future) and package.json data is added.

I am not very experienced with git branching, but it seemed like a good way to offer you the option to merge things separately.
Don't hesitate to let me know if there is a better way.