Implemented: Stances

Added: Basic stances (Aggressive, Guard (Hold Ground), Hold Fire, None (dummy), Return Fire)
Added: WorldCommandWidget (to be able to set said stances)
Added: WorldCommandWidget to ra (cnc will follow, later on)
Changed: Added support to AttackBase for firing with movement disabled + utility method ScanForTarget (used by stances)
Added: AssignUnitStance (attach this to unit-producing actors, together with what stances can be picked as 'default')

OpenRA.Mods.RA/AttackOmni.cs

@@ -38,7 +38,7 @@ namespace OpenRA.Mods.RA
 			DoAttack(self, target);
 		}
 
-		protected override IActivity GetAttackActivity(Actor self, Target newTarget)
+		protected override IActivity GetAttackActivity(Actor self, Target newTarget, bool allowMove)
 		{
 			return new SetTarget( newTarget );
 		}