Alter script parameters to be more PowerShell-y.

[pfaffle]

Rather than have a general "option" parameter which can be parsed in different ways, the script should define two different sets of parameters which are mutually exclusive, and alter the behavior of the script depending on which set is used.
http://blogs.msdn.com/b/powershell/archive/2008/12/23/powershell-v2-parametersets.aspx

Also, for required parameters, use the [CmdletBinding()] directive and specifically mark those parameters as required, rather than writing logic to check if they have a value.
http://technet.microsoft.com/en-us/magazine/jj554301.aspx