Handle default value set by setting value

[lucaslaurent04]

Can be used like this for identity\CenterOffice class:

'printer_type' => [
    'type'              => 'string',
    'selection'         => [
        'pos-80',
        'iso-a4'
    ],
    'description'       => 'Printer format to be used for PoS tickets.',
    'default'           => 'defaultSetting', // Use defaultSetting magic method
    'setting_default'   => 'iso-a4',         // Default value if setting does not exists
],

In this specific case the setting complete name is identity.default.center_office.printer_type