Bug 1032629 - APN Settings UX refresh

https://bugzilla.mozilla.org/show_bug.cgi?id=1032629
Definitely, the default APNs must contain all the APN in the apn.json database matching the MCC MNC codes as there might be several APNs. If you don't query the apn.json database you might be hidden some APNs (typically MVNO's). Remeber for a given pair of MCC MNC codes there might be several APNs.