New beta using Ren'Py 8

Hi all, we've updated this game to use Ren'Py 8, which is the latest version of the framework available. We've already tested the game, including mini-games, and fixed some minor alignment issues. Everything else should work as before, but since it's a big switch (the original game was released over 6 years ago!) we prefer to keep it in the beta channel for a while. Thanks to anyone who will give a try to the new version. The old version will remain available in any case, for people still running 16-bit systems.