Persistence

Thanks to boostchicken's diligence, it is now possible for modifications to the UDM variants to persist across firmware updates, so it's time to cut a release.

This release adds support on-boot-script persistence, multiple SAN support and miscellaneous fixes. If you've installed this previously, note that I've changed the installation directory to /mnt/data/udm-le so you'll want to update your system accordingly (and probably delete /etc/cron.d/lego if it still exists.

Thanks to @gtrabanco for bugfixes!