Allow for some effects to be granted more than once to the same target

[krbz999]

There are a good few cases where an effect can be granted more than once and should accumulate. For example, in FM, Victory Graves' Kinetic Buildup feature which grants +5 feet of movement.

If more options for effect application are ever added, it would be nice to be able to decide whether an effect overrides (default) or accumulates.