Polished the Dune 2000 shellmap to highlight both Carryalls and Sandworms

I polished the shellmap a little. The Atreides artillery now has it's turret facing

![image](https://cloud.githubusercontent.com/assets/756669/5538194/772ec33a-8aaf-11e4-9650-e93268d516f4.png)

towards the new Emperors outpost.

![image](https://cloud.githubusercontent.com/assets/756669/5538185/60591494-8aaf-11e4-8892-d3e80db538cb.png)

Also a carryall will deliver the harvester and replace any sandworm damage so that this plays continuously.
Woops, that crept in from https://github.com/OpenRA/OpenRA/pull/6880 which I based this on.