6066 Crate Prerequisites

Closes  #6066, #2587.

Also updated crate yaml for affected mods (RA and D2K).

Also adds YamlException on a GiveUnitCrateAction if it does not define any units to give.
```usedCells``` is manipulated witin the ```Activate``` function. Now sure why ```readonly``` was happy with the ```usedCells.Add(location.Value);``` action.

But shouldn't be ```readonly``` either way.