Fix __unicode__ of Distribution and ArticleType model
Fix __unicode__ of Distribution and ArticleType model

One of the names of the distributions contains characters with accents.
Printing this name causes a unicode error. To fix the error, only the
id of the Distribution or ArticleType is returned in the __unicode__
function.

UUDigitalHumanitieslab/texcavator,msassmann/texcavator,UUDigitalHumanitieslab/texcavator,msassmann/texcavator,msassmann/texcavator,UUDigitalHumanitieslab/texcavator,msassmann/texcavator