Review all TEI content types

[larkvi]

There was a lot of fiddling with content models to make everything nest properly. Review all content models in the ODD, with regard to:

• do content models for existing elements need to be changed?
• • if so, would this be desirable to change for all users of TEI? (submit change)
• are there constraints that need to be enforced that are not currently enforced?
• how would a model extension handle the content types, versus the accomodations made for existing monasterium data?

[larkvi]

seal/authen need to be revised per #55