Add scenario version and game engine version to show compatibility in the game UI

[Greenheart]

Ideas

• Follow semantic versioning for game client and scenario format. Update both versions at the same time.
• Build the game client with a version string
• Build scenarios with the same version string
• Potentially use metadata to determine if scenarios fail loading, and show friendly error messages.
• Maybe: maintain a CHANGELOG.md to document changes in every version, to avoid scenarios to get updated to newer formats.

[Greenheart]

Also add the commit hash, which will be useful for reporting bugs.