Re: [PATCH 13/13] [RfC] API for STK driver to signal executed commands.

Some modems are able to handle some proactive commands in their firmware or otherwise, if the command doesn't require input from user. Nevertheles ofono may need to update internal state or notify the user where necessary. With this api the driver can notify core that a command is being executed in the modem or that a command is finished executing and the TERMINAL RESPONSE has been sent to SIM. It would also be possible for a driver to handle a command.