Project file refactor (#819)

* Project file refactor

Move all the .csproj files to the new .NET Core style.
This doesn't make any difference for compiling for Framework,
but it does reduce a ton of useless boilerplate.

As an extension of this, killed a bunch of uncompiled & unmaintained .cs files.

Compiling for release (to profile) works now.
Removed AnyCPU targets from the solution file.

* Fix compiler warnings.

Robust.Server/Player/PlayerManager.cs

@@ -25,11 +25,13 @@ namespace Robust.Server.Player
     /// </summary>
     internal class PlayerManager : IPlayerManager
     {
+#pragma warning disable 649
         [Dependency] private readonly IBaseServer _baseServer;
         [Dependency] private readonly IGameTiming _timing;
         [Dependency] private readonly IServerNetManager _network;
         [Dependency] private readonly IReflectionManager _reflectionManager;
         [Dependency] private readonly IMapManager _mapManager;
+#pragma warning restore 649
 
         public BoundKeyMap KeyMap { get; private set; }