Draft: switchbin: support switching the path by property

Now there's a new property "trigger", that allows us to choose the selection mode between "caps" and "property". The default value is "caps" that represents previously known behaviour of the switchbin: to select path based on the caps. And now if the property "trigger" is set to "property", switchbin will select the path based on the value of the "current-path", that user is allowed to set in that mode.