tei to nlm updates, list type, validation for empty tags, nbsp on required empty tags.

 metadata,
    
    default article type added in the xsl
    extra attributes added to the defaul metadata.xml
    
    tei-to-nlm
    
    template for fn-group: line 265
    now recognize notes inside paragraph and hi, an attribute of id is added to, to link to the reference.
    ToDo: further development to improve finding footnotes
    
    template for list: line 412
    now include attributes to determine and assign the type of list
    
    template for list/item: line 442
    validation to avoid empty items tags
    
    template to cit: line 505
    validation to avoid avoid empty quotes tags
    
    template for ref: line 571
    dafult attribute link type added as uri.
    ToDo: parser to detect teh type of link attribute
    
    template for notes: line 661
    identifier for the reference added

    template for doTags: line 1004
    validation to put nbsp in a required empty tags, mostly for typos in the paper.