[osis-core] OSIS book abbreviations

[Harry Plantinga]

> Esth is the abbreviation for Greek Esther as well.
> 
> It's the same book, just a different versification.  AddEsth 
> is only for 
> those cases where the additions are to be identified independently.
> 
> --Chris

I don't think that's a good idea. If that's the case, we
don't know if Esth.2.2 refers to the verse as it appears
in Esther or as it appears in Greek Esther. If we're using 
the NRSVA as the standard, those are two different verses --
the one may have many words not appearing in the other, etc.

-Harry