Initial implementation of Sandworms (WIP; Need help with audio and animations)

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.
```csharp
[Desc("Does the attack type requires the attacker to enter the target's cell?")]
public readonly bool RequiresEnteringCell = false;
```