Add WMI 4 install prereq and link

Based on customer feedback

Author: alkohli

articles/databox/data-box-disk-deploy-set-up.md

@@ -38,6 +38,7 @@ Before you begin, make sure that:
     - Have [Windows PowerShell 4 installed](https://www.microsoft.com/download/details.aspx?id=40855).
     - Have [.NET Framework 4.5.1 installed](https://www.microsoft.com/download/details.aspx?id=30653).
     - Have BitLocker enabled. For more information, see how to [Enable BitLocker on Windows 2012 R2 systems](https://docs.microsoft.com/windows/security/information-protection/bitlocker/bitlocker-how-to-deploy-on-windows-server).
+    - Have [Windows Management Framework 4 installed](https://www.microsoft.com/en-us/download/details.aspx?id=40855). 
 
 ## Unpack your disks