Feature request: audio quality settings

[tox-user]

It would be very useful to be able to change audio quality. I assume that means changing bitrate. It would enable people to use qTox even when they are on a poor internet connection. There should probably be a few predefined values for the user to choose from, for example: high, medium, low, very low. Currently if someone is on a bad internet connection they might not be able to use qTox so they would have to switch to another messaging app that has lower internet usage.