Add a simple switch device

[Elock98]

• All nodes connected to the switch must be on the same subnet.
• It shall be possible for two or more switches to be connected.
  • If nodes are connected to the switches, then their subnets must all match.
    • It could be a good idea to store the active subnet in the switch.
    • We might want to have a switch connect protocol (SCP) that is sent every time there is a connection to the switch that is
      only handled by other switches and is ignored by all other devices.