Split off last bot modules

And dissolve AI namespace.
There would have been so little left in Common.AI,
that keeping it made no sense anymore.

OpenRA.Mods.Common/Traits/BotModules/Squads/StateMachine.cs

@@ -0,0 +1,52 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2018 The OpenRA Developers (see AUTHORS)
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+namespace OpenRA.Mods.Common.Traits.BotModules.Squads
+{
+	class StateMachine
+	{
+		IState currentState;
+		IState previousState;
+
+		public void Update(Squad squad)
+		{
+			if (currentState != null)
+				currentState.Tick(squad);
+		}
+
+		public void ChangeState(Squad squad, IState newState, bool rememberPrevious)
+		{
+			if (rememberPrevious)
+				previousState = currentState;
+
+			if (currentState != null)
+				currentState.Deactivate(squad);
+
+			if (newState != null)
+				currentState = newState;
+
+			if (currentState != null)
+				currentState.Activate(squad);
+		}
+
+		public void RevertToPreviousState(Squad squad, bool saveCurrentState)
+		{
+			ChangeState(squad, previousState, saveCurrentState);
+		}
+	}
+
+	interface IState
+	{
+		void Activate(Squad bot);
+		void Tick(Squad bot);
+		void Deactivate(Squad bot);
+	}
+}