Module used for both OPAC and intranet pages.
If this script has to modify the shelf content.
To know on which shelf to work.
Op can be: * modif: show the template allowing modification of the shelves; * modifsave: save changes from modif mode.
Load template with 'viewshelves param' displaying the shelf's information.
If the param shelves == 1, then add or delete a shelf.
If the param shelves == 1, then addshelf is the name of the shelf to add.