Update RunspaceConfiguration apis to use InitialSessionState instead

[proxb]

Reference PowerShell/PowerShell#2045

[proxb]

Looks like i can do something like this:

$ISS = [initialsessionstate]::CreateDefault()
$TypeFile = New-Object
System.Management.Automation.Runspaces.SessionStateTypeEntry -ArgumentList
'WindowsPowerShell\Modules\PoshRSJob\TypeData\PoshRSJob.Types.ps1xml'
$FormatFile = New-Object
System.Management.Automation.Runspaces.SessionStateFormatEntry -ArgumentList
'WindowsPowerShell\Modules\PoshRSJob\TypeData\PoshRSJob.Format.ps1xml'
$ISS.Formats.Add($FormatFile)
$ISS.Types.Add($TypeFile)
$Runspace = [runspacefactory]::CreateRunspace($ISS)