Constantia

This is a pull request for the blog to facilitate the implementation.

It includes a rewriting of the templating to treat the content between braces in the text nodes and in the attributes. It calls an xslt for the 'tei" content key. 

The models exemple give some extent to metadata and a starting library for tei.

@bug the 'order by' clause in the listArticles doesn't work
@todo treat mixed content in the templating
@todo calls xslt fo the content keys starting with "tei:"

Best regards !!  -`ღ´-