When the file is a reference or is a source of reference we show the icon in filemanager.
We should show the same in filepicker.

Show reference icon - always (repositories: coursefiles, local, user, recent?)
Show source icon in repositories: coursefiles, user.
Do NOT show source icon in server files (repository_local) in coursefiles subfolder (because we don't know whether it is current course or not)

Also show reference source and shortcut/aliases in filepicker 'select file' window the same way they are shown in filemanager