Default System Output

[adrum]

This changes the default system output, along without default output. If the devices also has an input, we set that as well.

In the future, it would be nice to able to option+click on the menubar to show/separate output devices from input devices.

Depends on #10.

[nimatrueway]

Hey @adrum, it's been almost a year and the maintainer seem to be too busy to process your PRs. Please consider creating your own fork with all these nice improvements. This is a great tool!