Add support for roll formulas in Active Event modifiers.

[PrototypeESBU]

Usage

A number of custom classes would benefit from complex formulas to represent bonuses to stats and abilities. Examples: eg. The Knight of St. Ydris class as an ability that adds +1+(floor(@level.value/2)) to damage based on the following talent:

Demonic Possession. 3/day, gain a +1 bonus to your damage rolls that lasts 3 rounds. In addition, add half your level to the damage bonus (round down).

System examples

ActiveEffects doesn't seem to allow variables or formulas by default in the modifier fields of effects, only numbers and strings. The popular 5e system does support this by extending the ActiveEvents class Similarly the module Dynamic Active Effects, also implements this, but only for the 5e system and one other.