remove "network_ai" and "network" controllers

DO NOT MERGE, has still bugs

Instead of having "network" and "network_ai" controller types to know whether we locally controll a side, we now have a "controller_client_id" attribute, and the cleints know whether a side is locally controlled by comparing "controller_client_id == local_controller_client_id". This has some advantages:
1) It very simplifies the serversided controller tweaks since the server can now send the same data to all clients if a controller client changes.
2) We dotn't show the information whether a side is local or networked in [stote_side]controller= this is useful becasue for most aplications people just want to know whether a side it human or ai, for example checks like controller == human work good in sp but not in mp. For those situation where one wants to know whether a side is local i want to add a seperate wesnoth.is_local(side) lua function.

TODO: remove side "name" attribute