Return a default value by get() when the corresponding value is not defined

[megahertz]

Hi Bastien.

Please let me suggest you to merge this request, which allows to simplify the following code:

let volume = config.get('volume');
volume = volume === undefined ? 1 : volume;

to let volume = config.get('volume', 1);

[de-luca]

Thanks @megahertz !