Generate default glowstone.yml from ServerConfig.Key

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*Edited by turt2live*

**Related Links:**
- None known. PR created due to support requests in `#glowstone` relating to configuration options.
- No ticket (none needed)
Would this change alone fit another PR tho?

I included it because it was related to the automatic generation of the config addressed in this PR and wouldn't break anything since none of the glowstone codebase relies on the ordering of the `ServerConfig.Key` enum.