Investigate having a GH-hosted 'game versions' file to set is_beta flag.

The idea here is we wouldn't need a new EDMC release in order to change what gameversions we think should set the is_beta flag.

Default to is_beta is True, unless the gameversion matches one the file says is live.

Simple pattern matching (substring? might want anchoring to start/end though) would allow, for e.g. "All with 'Fleet Carriers Update' are now live".