Be more explicit about the purpose of $DefaultValue in a Term definition

It appears to be unclear what the purpose is of having a $DefaultValue for a term definition in our JSON CSDL as, as stated in the specification as is, in our JSON CSDL a value MUST always be specified anyway. And while a $DefaultValue might be obvious for some terms, most notably boolean typed terms (read: tags) where the values is typically true, and there maybe a value for some enum and numerically based terms, this is less so the case for any of the other types.

The reference to it being for documentation purposes raised different questions.

On the other hand, if a term is of a structured type, default values of the individual structural properties are indeed implied in absence of the property, which is not the case for terms not being applied to any model element it could have been applied to, which further would speak to not having a $DefaultValue in terms potentially causing confusion.

Our XML CSDL however didn't require the value to be there, merely 'tagging' a model element with the annotation term would suffice, implying the DefaultValue specified in the XML CSDL. Therefore, arguably, the only remaining 'function' of this $DefaultValue is to allow for full fidelity round-tripping between our XML and JSON versions of the CSDL.