Seems to be a variation on CRC-64-ECMA.
This python version is of course very slow.
That should not be a big issue however, since
it is only required for serialising rather
small save game data.
Eventually the "download" command will be changed to
set the --no-install flag by default and "update" will
become --update-only. For now remain backwards compatible
to give people a chance to adjust their scripts and habits.
Fixes#18
In the future we might extend this with other features,
such as specific post-install things that some games
may require to work or preconfigured WINE settings.