There is an enum type for it ```JoinOptions Options```, which matches how PowerShell allows users to join a computer to a domain. But actually the integer value is not limited to those enums, so I expose this parameter to let users directly specify the mask value.

Please refer to:
1) PowerShell document: http://technet.microsoft.com/en-us/library/hh849798.aspx
2) Win32 API document: http://msdn.microsoft.com/en-us/library/windows/desktop/aa370433(v=vs.85).aspx