Turns GameTicker into an EntitySystem. (#4197)

* GameTicker turned into an EntitySystem

* Turns ClientGameTicker into an EntitySystem, turn NetMessages into events

* Change event names to be more consistent with the rest.

* YAML linter uses the dummy gameticker CVar override.

* Fix game ticker initialization order

* Dummy ticker won't spawn players.

* Fix character creation test

Content.Server/GameTicking/Commands/GoLobbyCommand.cs

@@ -6,6 +6,7 @@ using Content.Shared.Administration;
 using Content.Shared.CCVar;
 using Robust.Shared.Configuration;
 using Robust.Shared.Console;
+using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
 
 namespace Content.Server.GameTicking.Commands
@@ -21,7 +22,7 @@ namespace Content.Server.GameTicking.Commands
             Type? preset = null;
             var presetName = string.Join(" ", args);
 
-            var ticker = IoCManager.Resolve<IGameTicker>();
+            var ticker = EntitySystem.Get<GameTicker>();
 
             if (args.Length > 0)
             {