Public collections

Hi,

This patch adds an option that allows to display all public sub-collections even if root collections are private. This is useful in collections/browse and when collections are selected in advanced search. Without this patch, these public sub-collections are available directly, but can't be linked in these pages so user cannot know they exist. 

This patch is independant and modifies the previous ones.

Sincerely,

Daniel Berthereau
Infodoc & Knowledge management