P2P Tunnel improvements (#3039)

* Fix P2P Tunnels randomly resetting to ME
* Allow one way push and pull. Outputs can pull from the input side, input can push into outputs.

src/main/java/appeng/parts/p2p/PartP2PTunnel.java

@@ -160,6 +160,11 @@ public abstract class PartP2PTunnel<T extends PartP2PTunnel> extends PartBasicSt
 	@Override
 	public boolean onPartActivate( final EntityPlayer player, final EnumHand hand, final Vec3d pos )
 	{
+		if ( hand == EnumHand.OFF_HAND )
+		{
+			return false;
+		}
+		
 		final ItemStack is = player.getHeldItem( hand );
 
 		// UniqueIdentifier id = GameRegistry.findUniqueIdentifierFor( is.getItem() );