Add support for preset lopping & volume

Add support to preset the lopping button and the the volume e.g. in boards.json:

`        "sounds" : [
            {
				"file": "action_music1.ogg",
                "description" : "Action Music 1",
				"category": "Music / 3rd Party",
				"loop" : "true",
				"volume" : "",
            },`