Added support for tdAddDevice, tdRemoveDevice and tdGetErrorString
Added support for tdAddDevice, tdRemoveDevice and tdGetErrorString

tdAddDevice just adds an empty device with no name, protocol, device code, etc. Will add support for:
-tdSetName
-tdSetModel
-tdSetProtocol
-tdSetDeviceParameter
-tdLearn
Hexagon/node-telldus,Zebusch/node-telldus-zb,Hexagon/node-telldus,Zebusch/node-telldus-zb,Hexagon/node-telldus,Zebusch/node-telldus-zb