Set of fixes for Bluetooth volume control issues:
* split OS volume from A2DP device volume;
* added translations for additional popup required
to indicate what volume is being set;
* fixed issue that on some devices setting the lowest
volume level would set the highest in reality;
* fixed Bluetooth auto-turnoff functionality;
* minor code cleanup.
Adapted both codec and HFP profile to be able to work together.
Now it's possible to stream 2-way audio via HFP profile, but it
has to be integrated properly with EGD-7405
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.
