Splits AttackMove into trait and activity.

Moves them to subfolders/namespaces accordingly.

OpenRA.Mods.RA/Move/Move.cs

@@ -13,6 +13,7 @@ using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
 using OpenRA.Mods.RA.Activities;
+using OpenRA.Mods.RA.Traits;
 using OpenRA.Primitives;
 using OpenRA.Traits;