Steering the GUI and the modem according to
whether VoLTE is permitted for the active
SIM card's operator. This is done based on
the SIM card's IMSI string.
Additionally, made logging more consistent.
Introduced the new logic.
From now on, every button can be tri-state, that is,
OFF/ON/Transiting whereas the Transiting state is
marked with the 'cheking...' caption written on the
button.
1. Prepare Pure and Bell specific `Application`
classes and add them to `app` target:
- `products/BellHybrid/apps/Application.cpp`
- `products/PurePhone/apps/Application.cpp`
2. Update `CMakeLists.txt` files.
3. Move `ApplicationBell` implementation to Bell-specific
`Application` class and remove `ApplicationBell` files.
4. Change Bell apps parent classes from `ApplicationBell`
to Bell-specific `Application` class.
5. Rename `Application` to `ApplicationCommon` in the rest of the files.
