LibIPC: Rename base classes to IClientConnection and IServerConnection

This matches what we're already calling the server-side subclasses
better, though we'll probably want to find some better names for the
client-side classes eventually.

Servers/ProtocolServer/main.cpp

@@ -19,7 +19,7 @@ int main(int, char**)
         }
         static int s_next_client_id = 0;
         int client_id = ++s_next_client_id;
-        IPC::Server::new_connection_ng_for_client<PSClientConnection>(*client_socket, client_id);
+        new_client_connection<PSClientConnection>(*client_socket, client_id);
     };
     return event_loop.exec();
 }