Add ofono_sim_inserted_notify function to notify the core of SIM
insertion / removal.
Make every plugin generate a sim inserted event on start. For devices
with removable card, the event should be emitted after the
plugin detects such event. For devices that need to wait for SIM card
initialization, they can emit this event later.
Calypso firmware is just bizarre. It seems that if anything is sent
before CPI=3 to the DLC handling voice commands, the ATD will not return
to command mode immediately, but instead wait until connected / failed
condition occurs.
If CPI=3 is sent first, then calypso will go to command mode immediately
after ATD is issued and report CPI indications as usual.
