Enable input (e.g. mic) levels.

[TheJoelGray]

It would be very useful to be able to view and modify the input device (mic usually) the same way the master volume is displayed. The use case for this is when something (I still haven't tracked them all down) reduces a mic's setting in the background without letting the user know. In order to fix it, it takes far too many clicks to get to the system settings to fix it. Is that a possibility?