Make group membership check language agnostic

[bill-long]

Fixes #1006.

• Add a helper function to retrieve the SIDs of well-known AD groups such as Enterprise Admins and Schema Admins.
• Change SetupAssist to use IsInRole rather than parsing the whoami output. We could continue parsing the whoami and look for the SIDs, but IsInRole seems like a cleaner way to do this.

Note that Get-WellKnownGroupSid returns the SID for the Domain Admins group which resides in the domain that the computer is joined to. Is there a scenario where we would want a different Domain Admins SID?

I tested the helper function on a Spanish forest and it works, but I don't have Exchange installed in this forest to do a full test:

PS C:\> Get-WellKnownGroupSid "Enterprise Admins"
S-1-5-21-26643861-2199645782-2938786794-519
PS C:\> (New-Object System.Security.Principal.SecurityIdentifier(Get-WellKnownGroupSid "Enterprise Admins")).Translate([System.Security.Principal.NTAccount])

Value
-----
ESDOM\Administradores de empresas

Example CSV output in the successful case: