[tei-council] Make repository optional in msIdentifier

[Gabriel Bodard]

According to Sourceforge ticket 
http://sourceforge.net/tracker/index.php?func=detail&aid=2672530&group_id=106328&atid=644065 
(closed) "At rev 6477, content model has been changed as requested [to 
make repository optional], but a schematron rule has been added to 
enforce the requirement that at least one of the locating components 
must be present." In the guidelines, however (both the new release and 
the dev version), repository is still the only required element in that 
part of the schema. The schematron rule is however there.

I'm hoping that this bug is small enough that it can be shoe-horned into 
the release version as a last minute correction.

Best,

G