[Obo-format] Upcoming specification of internationalized string

[Alan R. <ala...@gm...>]

http://www.w3.org/2007/OWL/wiki/InternationalizedStringSpec

We save ourselves a lot of work if we either a) Just use this specification
or b) Define an explicit mapping of obo format strings to rdf:text and say
that the semantics are specified in this document.

-Alan