Added lidgren submodule, removed raknet code. Not yet compiling.
Converting code over to Lidgren from Raknet.

Taking the opportunity to move the dependency to the Engine.Shared project only where possible. Currently Engine.Server also has it, but only for the NetConnection property on the RemoteClient class.
Removed Lidgren dependency from Engine.Server
Got things compiling, but time-related code needs reconsidered & implemented
Listen server connections now get a networking instance created, so that it can create outgoing messages.
Times now use DateTime. Intervals are all TimeSpans instead of uint millis. Snapshots running off of ticks instead of times.
Sending messages to/from local players now correctly sets the message type, and skips past the byte of payload data containing this value.
Prevent a crash when SendToAllExcept had no one to send to
Tick interval gets a default value set. When connecting to a server, it tells clients its current tick.
New connections now actually added to ServerNetworking's Connections list
Ensure client starts off behind the server's time, by the lerp delay. Alas, this doesn't make things suddenly work.
Client's TickInterval was initially zero, and so until fully connected to a server, the client had been churning away, updating its CurrentTick value, so that it would be well ahead of the server's.
Added the Artemis Entity Component System as a submodule, having reworked it to compile under .NET 3.5