Return unicode representation for descriptions.

Since those go into the catalog, we need to have a unicode here and  no
I18NDict which can't be serialized to JSON later.

A rebuild of the portal_catalog will fix any possible issues for
existing content.

src/pkan/dcatapde/content/dcat_catalog.py

@@ -212,7 +212,7 @@ def Title(self):
         return unicode(self.dct_title)
 
     def Description(self):
-        return self.dct_description
+        return unicode(self.dct_description)
 
 
 class DCATCatalogDefaultFactory(DexterityFactory):

src/pkan/dcatapde/content/dcat_dataset.py

@@ -244,7 +244,7 @@ def Title(self):
         return unicode(self.dct_title)
 
     def Description(self):
-        return self.dct_description
+        return unicode(self.dct_description)
 
 
 class DCATDatasetDefaultFactory(DexterityFactory):

src/pkan/dcatapde/content/dcat_distribution.py

@@ -158,7 +158,7 @@ def Title(self):
         return unicode(self.dct_title)
 
     def Description(self):
-        return self.dct_description
+        return unicode(self.dct_description)
 
 
 class DCATDistributionDefaultFactory(DexterityFactory):

src/pkan/dcatapde/content/dct_licensedocument.py

@@ -55,7 +55,7 @@ def Title(self):
         return unicode(self.dct_title)
 
     def Description(self):
-        return self.dct_description
+        return unicode(self.dct_description)
 
     def title_for_vocabulary(self):
         """Return a title suitable for vocabulary terms."""

src/pkan/dcatapde/content/dct_location.py

@@ -50,7 +50,7 @@ def Title(self):
         return unicode(self.dct_title)
 
     def Description(self):
-        return self.dct_description
+        return unicode(self.dct_description)
 
     def title_for_vocabulary(self):
         """Return a title suitable for vocabulary terms."""

src/pkan/dcatapde/content/dct_mediatypeorextent.py

@@ -52,7 +52,7 @@ def Title(self):
         return unicode(self.dct_title)
 
     def Description(self):
-        return self.dct_description
+        return unicode(self.dct_description)
 
 
 class DCTMediaTypeOrExtentDefaultFactory(DexterityFactory):

src/pkan/dcatapde/content/foaf_agent.py

@@ -51,7 +51,7 @@ def Title(self):
         return unicode(self.dct_title)
 
     def Description(self):
-        return self.dct_description
+        return unicode(self.dct_description)
 
 
 class FOAFAgentDefaultFactory(DexterityFactory):

src/pkan/dcatapde/content/skos_concept.py

@@ -57,7 +57,7 @@ def Title(self):
         return unicode(self.dct_title)
 
     def Description(self):
-        return self.dct_description
+        return unicode(self.dct_description)
 
 
 class SKOSConceptDefaultFactory(DexterityFactory):

src/pkan/dcatapde/content/skos_conceptscheme.py

@@ -50,7 +50,7 @@ def Title(self):
         return unicode(self.dct_title)
 
     def Description(self):
-        return self.dct_description
+        return unicode(self.dct_description)
 
 
 class SKOSConceptSchemeDefaultFactory(DexterityFactory):