Fix utf-8 path problem on Windows.
Remove the import of NATFirewall.
Merge pull request #434 from LipuFei/rm-import-natfirewall

Remove the import of NATFirewall.
Merge pull request #431 from LipuFei/fix-shutil-utf8

UTF-8 paths for shutil functions.
Merge remote-tracking branch 'upstream/devel' into devel