Folder "Recycle_bin" must be Hidden with attribute "H" if Windows OS

Useful if the Repo is accessed directly from "explorer" Windows for
others user who don't use Pydio.
In this case the folder "Recycle_bin" must be Hidden.
Merge pull request #549 from Ellega/hide.recycle_bin2

Folder "Recycle_bin" must be Hidden with attribute "H" if Windows OS