ENYO-1020: `DirectorySelectorPopup` is now `FileChooser`

- `DirectorySelectorPopup` is now `Ares.FileChooser` defined by
  `utilities/source/FileChooser`
- Move manual `style:`  into `Ares.css` as `.ares-filechooser*`

Enyo-DCO-1.1-Signed-off-by: Francois-Xavier KOWALSKI <francois-xavier.kowalski@hp.com>