[rilmodem][WIP] Introducing preferred network selection mode setting

Enables forcing connection to GSM, LTE and UMTS network types
if available.

Signed-off-by: jussi.kangas@tieto.com
[rilmodem][WIP] Releasing radio data when removing

Adding missing unreferencing of radio data in order to
avoid possible memory leak.

Signed-off-by: jussi.kangas@tieto.com
[rilmodem][WIP] Starting up radio interface

Publishes rilmodem radio interface to Ofono API.

Signed-off-by: jussi.kangas@tieto.com
Merge pull request #10 from jkangas/master

Request for pulling prefeffed network type selection to main branch