XTCE13 — Cleanup Container EntryList element by deprecating IndirectParameterRefEntry

The IndirectParameterRefEntry is a clever construct that has the potential to be useful, although I am not aware of anyone who has used it.

I suggest that we consider removing it because it is a limited case of the more general case solved by the IncludeCondition element. The IncludeCondition can provide this functionality and a lot more. As a result, this element is effort for implementers that doesn't add anything really "new". In addition, it leaves a case where the need is addressed in more than 1 way - which is generally not the best idea.

IndirectParameterRefEntry scopes to a 2.0 proposal

The request for modification of the IndirectParameterRefEntry element is a not a backwards compatible change to the XTCE data model. This type of change cannot be done by a minor revision task force. This would need to be something that is handled by a potential 2.0 RFP.