[osis-core] Reference Syntax Proposal

[Harry Plantinga]

> I an with Troy that "Matt.1.6a" should not be allowed in any case
> (unless the "standard" reference system actually specifies Matt.1.6a as
> an individual reference and does NOT have a "Matt.1.6").
> 
> However, unless the "standard" reference system actually defines a four
> level system of identifiers then "Matt.1.6.a" would not be correct
> either.

If we are using Matt.1.6.a and Matt.1.6.b as means of identifying two
pieces of a split element, corresponding to Matt.1.6, it seems to me that
we would have to allow Matt.1.6.a even if it is not in the reference system
definition.

-Harry