Fix minor issues

- Force output by Default Encoding
- Reject Executing path is begin with UNC path
- There is no need to convert to UTF8 after Uri.EscapeDataString
- Fix commands 'ls -la' will execute 'ls' and 'la' issue, and not, it will split by '\n'

TODO: if commands contains '\\\n' it may occur an error, so it need to replace by ' ', and needs to confirm