Enhance autoconfigure

This MR does two things

• instead of assuming a 6 digit IMSI use the preferred operatator mcc/mnc from the sim. This moves the responsibility for figuring out whether it's a 5 or 6 digit mccmnc to modem manager. With this my 5 digit provider is looked up correctly.

• Use the configuration from the type=mms APN in m-b-p-i instead of the active bearer. While this one is needed to pick up the right parameters for my provider it fails later on since this isn't the one used by the active bearer:

mmsd-tng[13480]: ../plugins/modemmanager.c:set_context() Current Context APN: pinternet.interkom.de, mmsd-tng settings MMS APN: internet
mmsd-tng[13480]: ../plugins/modemmanager.c:set_context() The modem is not connected to the correct APN!
mmsd-tng[13480]: ../plugins/modemmanager.c:bearer_handler() Set MMSC: http://10.81.0.7:8002, Set Proxy: 195.182.114.52:8080, Set MMS APN: internet
mmsd-tng[13480]: ../plugins/modemmanager.c:bearer_handler() At Bearer Handler: path /org/freedesktop/ModemManager1/Modem/9 active 1 context_active 0
mmsd-tng[13480]: ../plugins/modemmanager.c:bearer_handler() Error activating context!
mmsd-tng[13480]: ../src/service.c:mms_service_bearer_notify() service=0xaaaac0f4ef40 active=0 iface=(null) proxy=(null)
mmsd-tng[13480]: ../plugins/modemmanager.c:mmsd_get_all_sms_timeout() Removing timeout to mmsd_get_all_sms()

@kop316

• whos responsibilty is it to connect to the right APN? Would mmsd bring that up?
• should I drop the last patch since for the moment since fixing mccmnc matching is already an improvement?