Add newlines to the ends of Apache 2.0 and GPL* templates

This adds newlines to the ends of the files `apache-2.0.erb`, `gpl-1.0.erb`, `gpl-2.0.erb`, and `gpl-3.0.erb`.  Some people (myself included) enjoy having newlines at the ends of their files, so it will be nice to not have to add a newline at the end of the file manually.