About proposal #83

This made the item.pt and container.pt parts (widgets, groups, folder_listing) easy to override part by part by a subpackage.  This way, it is easy to override the way "folder_listing" will appear on a defined content_type without defining a new View form for the content_type...

By mistake, I already pushed a part of this on the master...  So, if it is ok, just push this pull request, if not, please remove my last commit on the master or I will do it ;-)

But, please merge ;-p

Gauthier