[tei-council] some more class changes

[Lou Burnard]

1. Changed content model of <relatedItem> to reference   model.biblLike 
and model.pointerLike rather than their members

2. Added <distributor> to  model.imprintPart  and removed it from direct 
membership in model.biblPart

3.  Made model.lLike a subclass of model.divPart and removed it from 
direct membership in model.divPart

4. Abolished macro.fileDescPart. It's only used once, and it breaks 
generation of tei_bare.