update QtBearer NetworkManager backend API

Task-number: QTBUG-41747

Change-Id: Idb4afea0215b94957a11895c7db97a72ae680804
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>
Add better mobile connections to QtBearer NetworkManager backend.

Task-number: QTBUG-41807

Change-Id: Ifb5904d4887111416b4bb1a32d6d056029186f5c
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>