Apply Weak/Elite adjustment to creature during _copy

[Jnosh]

Weak/Elite are applied as an initial step before any _copy modes or merges with the target data.

Named the property creatureAdjustment for now but I am open to alternative suggestions. Alternatively, could also introduce a _copy modifier for use in _mod * entries instead.

Example:

{
    "name": "River Devil",
    "source": "ToK",
    "page": 7,
    "_copy": {
        "name": "Sea Devil Scout",
        "source": "B1",
        "creatureAdjustment": "Weak"
    }
}