Fix some issues in the custom game settings schema

[netux]

• Allow for map objects with variants. Very complicated JSON schemas code, but in plain english:

  The change allows enabledMaps and disabledMaps to contain both strings and objects with a single property (map name), of value array of strings, where each string must be a valid map variant for the map.

• Remove special case for the "general" hero schema, which was actually causing the schema to be invalid
• Regenerate schema with these changes

Also adds a settings.opy.json to examples/, which I used for testing.