bundles obviate folders-first policy option

10.21: adde/fs/mac's bundle idea obviates folders-first policy option:
. instead of having a folders-first policy option,
the file system should be more like
mac's bundle system
where each folder has the option of
declaring itself to be either
a folder or a bundle .
. so then, in a file system window,
folders can be listed before files,
but the bundles are treated like files .