D2k: Sandworms implementation

Using Mailaender's code as basis, this is my implementation of the sandworm behavior. It is still WIP, but you can get an idea of how it looks from the shellmap.
Luckily https://github.com/OpenRA/OpenRA/wiki/Traits#cloak is already configurable with CloakTypes. Mines, sub marines etc. they all use the same trait, but work independently from another.