Discovery of not onboarded Eve devices

Right now the onboard procedure require an onboard parameters to be specified and then the controller can accept the device. 

It has some drawbacks: 

        1) If I specified wrong parameters I can't easily debug the problem, especially if I don't have the interaction with the device

        2) The device might be slow to power up and boot the network. 

        3) Just wait some time isn't that reliable mechanism for unexperienced user

I suggest to have some discovery - namely: 

      A device reports some data about itself upon connecting to the controller. E.g. its hw model , some key and IP (or controller gets its IP)

      I can list such devices and their availability

      I can onboard a specific device from the list using my certs/some other data as it works now. 

      I can set a mode of "onboard any device with key" - this way an automation may happen