Packages should not load in full trust

[phogue]

Protocol assemblies are currently loaded in Procon's instance AppDomain which runs in full trust.

This should be modified to load these assemblies in an AppDomain which only has access to protocol package path and UDP/TCP network access on the port to the game hostname. This will mean adding a new connection will require all existing connections to restart, but the security is worth the inconvenience.

It's a slightly increased level of trust from a plugin, but only because it needs to do more. It's not exactly a plugin, which is why it's handled elsewhere.