Debugging option

Preparing for the plugfest I noticed 
https://github.com/bberliner/openc2-json-schema/blob/master/src/test/resources/commands/good/query_features_extension_args_number.json has an extension arg for debugging. I think we should have a standard debugging parameter in args. As a security geek
 I think “production” interfaces should provide as little info as possible ie no need to assist hackers -but as a developer writing/debugging I find the extra info on error conditions is quite helpful. So the answer to my dual personality is a debugging option
 to use in development but ignore in production. So I propose we add this argument to the language spec. 

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