Modernize the Net-Interface code

[tribad]

Some of the network code is somewhat outdated.
So it would be a good idea to modernize this.

This is not about the packages created and send over the wire. But the basic connection management stuff.

[tribad]

Change all pointers to node_t into references.

[tribad]

The only thing that is not working at the moment is server list.
I think there are some problems with copying with pointers to node_t.
So next step to check that.