Added support for exploding dice with manual rolls - likely fix issue #464

[inxaos]

Added a setting to support Exploding Dice being manually entered (useful for systems such as Savage Worlds / SWADE). Likely resolves #464

Previously, when the die value entered equals the maximum die value, the "exploding" dice are automatically generated afterwards behind the scenes and cannot be entered manually. This setting removes the maximum value validation from the Roll Prompt form, allowing the total of all exploded dice to be entered as a single value, which works properly for further calculations.