[GP-1842] Update the Cellular code to use SIM IMSI for Verizon detection

See merge request !14

The certifications lab uses special SIM cards with non-Verizon ICCID numbers
and Verizon IMSI numbers (MCC/MNC prefixes or PLMN IDs). Update the code to
detect Verizon properly for such "special" SIM cards.

Renamed the functions to better represent their behavior and purpose.

This project uses tabs, not spaces. Make the indentation consistent.

fn980: use custom iccid command

See merge request !13

MTX-3534 Fix crashes on 64-bit platforms

See merge request !12

The char* pointer retruned from strrchr() function was assigned to int variable tmp.
On 64-bit platforms where pointer is 64-bit and int is 32-bit 2 bytes were lost and
consequent dereference of sliced pointer lead to segmentation fault. As a solution
the type of temporal variable is changed to char*.

[MTX-3489] mPower Oct20: Porting "LNA7 Intermediate Release" changes

See merge request !11

Ported the Verizon LTE SMS format workaround from LNA7 to L4G1.