Add a flag "Marked as favorite" for medias in the Library
Favorite feature : the mediator of the box should be allowed to editorialize his / her library and to flag a book as "favorites" or "librarian's choice". The tagged books would then appear on the front page when the user click on a filter "Trier par "choix du libraire". This filter should appear close to the Title and authors filters only if at least one book is tagged. Same kind of feature as #561