Feature Request: Add helper method to parse PropertiesChanged

[maltegrosse]

Hi, wouldnt it be helpful to have a helper method to parse the properties changed signal?

PropertiesChanged(s interface_name, {sv} changed_properties, as invalidated_properties):
interface_name: name of the interface on which the properties are defined
changed_properties: changed properties with new values
invalidated_properties: changed properties but the new values are not send with them

something like:

func (d *dbusBase) parsePropertiesChanged(v *dbus.Signal) (interfaceName string, changedProperties map[string]dbus.Variant, invalidatedProperties []string, err error) {
	if len(v.Body )!= 3{
		err = errors.New("error by parsing property changed signal")
		return
	}
	interfaceName, ok := v.Body[0].(string)
	if !ok {
		err = errors.New("error by parsing interface name")
		return
	}
	changedProperties, ok = v.Body[1].(map[string]dbus.Variant)
	if !ok {
		err = errors.New("error by parsing changed properties map name")
		return
	}
	invalidatedProperties, ok = v.Body[2].([]string)
	if !ok {
		err = errors.New("error by parsing invalidated properties")
		return
	}
	return
}

[jsouthworth]

Sounds like a good addition. If you would like to contribute this, please open a PR so we can discuss further.

[damianmyers2]

Saw this issue while working on another project, seemed like a fun thing to tackle