Update the Invoke-DiscoverDevice Python and PowerShell scripts to handle network devices

[grantcurell]

Right now the discovery scripts (Invoke-DiscoverDevice.ps1 and invoke_discovery_device.py) have hard coded JSON which they then convert to native types. The community string is hard coded in the JSON and we do not provide a way to modify it.

Update

I saw we don't actually include it as an option, but it is there in the discovery payload.

[grantcurell]

This has been addressed in the powershell code. This issue is now a dup of #119