[osis-core] new half-verse milestonePt type?

[Chris Little]

I realize this is rather specialized and perhaps outside the scope of 
what BTG wants to handle, but I'll propose it anyway since it doesn't 
require much.

Anglo-Saxon poetry includes Beowulf, the Anglo-Saxon Chronicle, and, of 
relevence to BTG, Codex Junius, which itself includes Anglo-Saxon verse 
adaptations of Genesis, Exodus, and Daniel.  Anglo-Saxon poetry 
recognizes a half-verse point that is rendered in print as 3-4 extra 
spaces.  Some other forms of poetry used in other languages also mark a 
half-verse, so this does apply outside of just Anglo-Saxon, but I don't 
know specifics.

So I'm requesting the addition of a "half-verse" value to the 
milestonePt type, or "halfVerse" if we want to avoid hyphens.  Some 
prose explanation would be deserved to clarify that this is a point and 
not a spanm so it cannot be used to mark the medial character in Hebrew 
verse.

--Chris