The mirror selector is a sub part of the volume slider. This could be
changed in the future to have the slider be a top level component that
contains both selector and slider.
For now the way to go is to have the mirror device and audio device
selectors as different components instead of trying to inherit from a
single component and filling in the necessary function calls.
This is because some function calls are nested inside other components
and would be very messy. Perhaps in future commits the selectors will
inherit from a single parent.
Setting the default audio profile has also been moved into the separate
dialog box. This should not change anything and no bugs were found in
testing, however I have no idea how objects in QML/C++ are initialized
or if our current codebase is created with this in mind.
Vasily