Wireless push-button

[sovcik]

Current wire-button adds unnecessary cables to the whole system.
Goal is to implement wireless-push button. E.g. using supercheap 433MHz trasmitters/receivers.

This will require:

1. each button to have unique identifier, so if there are multiple Tern systems running then RasPi can identify ITS button
2. some kind of configuration on Tern side - push-button identifier