This commit adds a combo box for selecting ports.
Overall this implementation could have taken two paths:
* Implement port selection as combo box.
* Implement port selection as a button.
I went for the first option as is done in selecting card profiles over the
second method used for selecting devices for streams. This seems more like
how a config option should be presented as opposed to a runtime type thing.
This makes the default button work on sinks/sources, allows the drop
down to actually change the sink/source and removes the old menu code.
Some names and such are fixed in the glade file too.
Colin Guthrie