Implement networkStatusQuery and signalStrengthQuery API methods

Open-webOS-DCO-1.0-Signed-off-by: Simon Busch <morphis@gravedo.de>
Rework subscription processing to be done as early as possible

Open-webOS-DCO-1.0-Signed-off-by: Simon Busch <morphis@gravedo.de>
Implement support for service group subscriptions

Open-webOS-DCO-1.0-Signed-off-by: Simon Busch <morphis@gravedo.de>
Fix several wrong service reponse message

Open-webOS-DCO-1.0-Signed-off-by: Simon Busch <morphis@gravedo.de>