New saving system with proper waiting for file flush

Command context for servers now supports Respond()
Chat manager now treats the steam ID Sync.MyId as a local destination, and processes the event accordingly.
Save makes better use of Task<>
Restart actually waits for save
PlayerCollectionExtension uses a dictionary lookup for TryGetBySteamId
Shutting the UI window properly closes Torch
Torch Dispose renamed to Destroy, VRage Dispose marked as obsolete (do not use)

Torch.Client/TorchClient.cs

@@ -66,9 +66,9 @@ namespace Torch.Client
             SetRenderWindowTitle($"Space Engineers v{GameVersion} with Torch v{TorchVersion}");
         }
 
-        public override void Dispose()
+        public override void Destroy()
         {
-            base.Dispose();
+            base.Destroy();
             _startup.DetectSharpDxLeaksAfterRun();
         }