Change the location where the Worker writes its local files so that it
follows the XDG specification (instead of writing to the current working
directory).
- Linux: `$HOME/.local/share/flamenco`
- Windows: `C:\Users\UserName\AppData\Local\Flamenco`
- macOS: `$HOME/Library/Application Support/Flamenco`
NOTE: The old files will not be loaded any more. This means that if
nothing is done and the new worker is run as-is, it will reregister as a
brand new worker. Move `flamenco-worker-credentials.yaml` and
`flamenco-worker.sqlite` to the new location to avoid this.
The add-on code was copy-pasted from other addons and used the GPL v2
license, whereas by accident the LICENSE text file had the GNU "Affero" GPL
license v3 (instead of regular GPL v3).
This is now all streamlined, and all code is licensed as "GPL v3 or later".
Furthermore, the code comments just show a SPDX License Identifier
instead of an entire license block.
