Split Locomotor trait from Mobile

Add GrantConditionOn*Layer traits

This allows to
- drop some booleans from Locomotor
- drop a good part of the subterranean- and jumpjet-specific code/hacks from Mobile
- grant more than 1 condition per layer type (via multiple traits)
- easily add more traits of this kind for other layers

OpenRA.Mods.Common/Traits/Conditions/GrantConditionOnTunnelLayer.cs

@@ -0,0 +1,26 @@
+#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
+
+using OpenRA.Traits;
+
+namespace OpenRA.Mods.Common.Traits
+{
+	public class GrantConditionOnTunnelLayerInfo : GrantConditionOnLayerInfo
+	{
+		public override object Create(ActorInitializer init) { return new GrantConditionOnTunnelLayer(init.Self, this); }
+	}
+
+	public class GrantConditionOnTunnelLayer : GrantConditionOnLayer<GrantConditionOnTunnelLayerInfo>
+	{
+		public GrantConditionOnTunnelLayer(Actor self, GrantConditionOnTunnelLayerInfo info)
+			: base(self, info, CustomMovementLayerType.Tunnel) { }
+	}
+}