Switched to Apache2 license, added README, removed useless file.

Is everybody okay with this? As far as I'm aware, AdvDuplicator's license wasn't discussed, but this is necessary for the workshop. There are some other people we need to ping, TAD2020 isn't on GitHub but if I recall is the principal author. @AT-Kenny and @Kadah have also contributed code to this repository but not agreed to a license change.