cleanup and consolidation

[flitzi]

• made acPlugins4net.dll signed
• set version of acPlugins4net.dll to 2.0: the major version should match the acServer UDP protocol version, minor should be changed at least for each release
• AcServerPluginManager: removed ServerName, Track, TrackLayout Properties (use MsgSessionInfo instead)
• AcServerPlugin: removed some obsolete properties
• app.config added load_server_cfg (default 1): set to 0 when plugin is run as an external plugin in this case ac_server_port, ac_server_host, plugin_port and max_clients should be set manually in app.config
• app.config added max_clients, only needed if settings are not loaded from server cfg (plugin run as external plugin)
• adjusted app.config of Admin2ChatPlugin and MinoRatingPlugin to include all settings that can be set
• adjusted Main methods of Admin2ChatPlugin and MinoRatingPlugin, so that additional plugin configured in app.config are loaded
• changed Admin2ChatPlugin to .NET 4.0 Client Profile