Player post-spawn hook and player ghosting controlled by preset (#2734)

* GamePreset: Add a hook to catch all player spawns for modification.

Unless someone makes the entire job system unpluggable, this is what you get...

* GamePreset: Is now in control of voluntary ghosting

* Clean up ghost code to only rely on a player's Mind

Content.IntegrationTests/DummyGameTicker.cs

@@ -3,7 +3,9 @@ using System.Collections.Generic;
 using Content.Server.GameTicking;
 using Content.Server.Interfaces.GameTicking;
 using Content.Shared.Roles;
+using Content.Server.Mobs;
 using Robust.Server.Interfaces.Player;
+using Robust.Server.Interfaces.Console;
 using Robust.Shared.Interfaces.GameObjects;
 using Robust.Shared.Map;
 using Robust.Shared.Timing;
@@ -49,6 +51,11 @@ namespace Content.IntegrationTests
         {
         }
 
+        public bool OnGhostAttempt(Mind mind, bool canReturnGlobal)
+        {
+            return false;
+        }
+
         public void MakeObserve(IPlayerSession player)
         {
         }