Property visibility

[andreareginato]

Some properties must be visible only from the device creator. For example in a camera, we do not want the final user to be able to update the camera URI. Also in this case think if could be better to make a device component specialization or if its easy to add to the device component and the API. If used only from the camera, maybe we need to power up the camera widget. See ussue #40 alway for the camera case.