Win Server 2012 detection and MSMQ installation

ServerManagerCmd.exe seems to be excluded from Windows Server 2012 in favour of using PowerShell commandlets.  "ServerManagerCmd.exe -install" changes to "PowerShell Add-WindowsFeature".

Related post on the forum:
https://groups.google.com/forum/#!topic/masstransit-discuss/CrYdIa9w3QE