Fix for #215 + minor additions

[MurrayR0123]

• Check added for null values returned by Child Jobs + Try/catch for switch statement to save results to avoid hard fail of Get-TargetData
• Minor increase in default timeout for jobs to 900 seconds (My testing found it wasn't long enough to allow Get-FileHash.ps1 to complete during more demanding operations)
• Fix to Get-Targets.ps1 - remove $HostNameRegex on line 29 as default value of "*." was resulting in no target devices matching and in turn no target devices being returned by Get-Targets. Replaced with a check to validate the ObjectClass of an AD object found by Get-ADComputer is "computer"