BugLink: https://launchpad.net/bugs/680810
Some laptops have 'Internal Mic 1' exposed as an 'Input Source', e.g., Dell
XPSM 1530, so handle these, too.
Signed-off-by: Daniel T Chen <crimsun@ubuntu.com>
Completely rework mixer logic. This now allows controlling a full set of
elements from a single sink's volume slider/mute button.
This also introduces sink and source "ports" that can be used to choose
different input or output ports with the UI. (i.e. "mic"/"line-in" or
"speaker"/"headphones".
The mixer paths and device maps are now configered in external
configuration files and can be tweaked as necessary.