[osis-core] headers & refSystems

[Chris Little]

I'm still really confused about the usage of headers (as outlined in my 
previous message on the topic) if anyone could clue me in on their usage.

Also, what is the usage of refSystem(s)?  Why are these not a part of 
work, and why do they need all the same element types as works?

Also, would it make sense to enumerate some standard refSystems for people 
to use so that they don't invent their own conflicting systems?  I have in 
mind things like beyond just "Bible" but like "Dictionary", 
"Lexicon.Greek.English", "Devotional.Daily", or "Index.Topical".  This 
helps to set up standard fall-backs.  E.g. if a document references 
something in a document using "Dictionary.Bible" as its refSystem but that 
specific work is unavailable, another "Dictionary.Bible" will be used, or 
another "Dictionary" if that is unavailable.

--Chris