Tweaked manual configuration option (e. g. for "Series C" model names)

[Reinboeng]

Older devices such as my 2010 C7700 may report a generic modelName 'Samsung DTV DMR'. The code change allows to use the manual configuration option (via usn) of the plugin. This will solve #56.

Configuration: {     "platform": "SamsungTVControl",     "devices": [         {             "usn": "uuid:nnnn",             "name": "Samsung TV",             **"modelName": "UE46C7700WSXZG"**,         }     ] }

Debug Output: deviceDescription: { deviceType: 'urn:schemas-upnp-org:device:MediaRenderer:1', friendlyName: 'TV-46C7700', manufacturer: 'Samsung Electronics', manufacturerURL: 'http://www.samsung.com', modelName: '**Samsung DTV DMR**', modelNumber: 1, modelDescription: 'Samsung DTV DMR', UDN: 'uuid:nnnn', icons: [ ....