SqlSetup: Add support for sysprepped SQL Server.

It is possible to prepare SQL Server most of the way with SysPrep (https://msdn.microsoft.com/en-us/library/ee210754.aspx).

This allows partial installation of SQL Server to a machine that will be sysprepped as a template (with /ACTION=PrepareImage for instances, /ACTION=PrepareFailoverCluster for failover clusters), then the installation can be completed on the restored images (with /ACTION=CompleteImage for instances, /ACTION=CompleteFailoverCluster for failover clusters).

This could be modelled as:

xSQLServerSetup SQL {
    ...
    SysPrep = 'True'
}

The default value would be 'False'.

Set-TargetResource can then proceed as follows:

Start with the SqlSetup resource and its Set-TargetResource implementation, using the issue's SysPrep state table as the behavioral specification. Review how xSQLServerSetup exposes resource properties and how the existing install and failover-cluster actions are selected. Done means the SysPrep setting supports the listed prepare, complete, no-action, and error states for instances and failover clusters.