Make repairing buildings and units grant experience

Using the repair button and repair pad, not using engineers and mechanics.

OpenRA.Mods.Common/Activities/Repair.cs

@@ -49,6 +49,13 @@ namespace OpenRA.Mods.Common.Activities
 
 			if (health.DamageState == DamageState.Undamaged)
 			{
+				if (host.Owner != self.Owner)
+				{
+					var exp = host.Owner.PlayerActor.TraitOrDefault<PlayerExperience>();
+					if (exp != null)
+						exp.GiveExperience(repairsUnits.PlayerExperience);
+				}
+
 				Game.Sound.PlayNotification(self.World.Map.Rules, self.Owner, "Speech", repairsUnits.FinishRepairingNotification, self.Owner.Faction.InternalName);
 				return NextActivity;
 			}