network-subsystem: DIfferenciate between receive and send package types

network::UdpConnection needs to know the types of both received and
sent package types, therefore a new template parameter was added.

Its implementations network::NetworkClient and network::ClientSession
were updated accordingly.
network::NetworkServer: Bugfix: Wrong callback when sending packages

The wrong handler was specified when sending data over an socket,
resulting in faulty behavior. This was the original reason why an
assert on the expected and actual nBytesSent was not possible
in the callback… ;-D
network::NetworkClient: Use ObjectManager to send state updates
Extended dummy server for state sync

Using the previous NetworkServer extension, the server implementation
was extended to sync the client and server states using the ObjectManager.