Allowing external hardware routers/emulators

[LencigGaer]

Enable SEED emulated topologies to connect with these hardware and emulations.

It should be possible to define the corresponding router or host in SEED as an external_component (or something similar) and then SEED should perform all the necessary steps to prepare connecting these devices. This external_component should also take optional parameters to configure the interface(s), IP(s) and MAC address(s). Furthermore, SEED should output an according configuration in a uniquely identifiable folder (in case of SCION this should contain at least the topology.json file and the keys).

So probably something similar to the RealWorldRouter but with support for SCION as well.