This PR implements support for reading and writing alternate data streams on Windows.
For now, the option is disabled by default and needs to be enabled with `--enable-ads-backup`. After this option is set, Duplicati will also extract any alternate datastreams from the filesystem and include them in the backup.
By default, ADS elements will be restored, but `--disable-ads-restore` can be used to ignore any ADS elements during the restore process.
This fixes#189
Kenneth Skovhede
a4820ccb62