ISIS-537 Put the "clear all bookmarks" link in the panel-footer. The panel-body may be used for some help text later
ISIS-537 Use the panel-body to show a help text, e.g. "You have no bookmarks" when BookmarkedPagesModel is empty

Use InlineEnclosure to hide the panel-body when there is no help text, and the panel-footer when there is no "Clear all" link