Restart lobby resurrection

[Bios-Marcel]

TODO

• Introduce optional encryption

  Forcing this might break existing deployments and a default secret for encryption would useless.
  Generating a secret based on machine details, such as a MAC Address might be unreliable in
  a world with ephemeral VMs and Docker containers.

• Don't accept new connections during shutdown
• Write unit tests
  • UserSession Changes
    • GetPlayer
    • kickPlayer
  • Resurrect
    • Make sure the lobby is fully functional, simulate gameflow with real sockets

An issue I encountered is, that the current implementation becomes useless once a user manually pressed F5. To solve this, a custom lobby gone page is required OR the lobby needs to be able to show even for an empty lobby.

The latter would be more consistent UI wise. But this means that upon resurrection, the lobby needs to reload, as some of the templated state won't be available.

Fixes #371