Enhancers and Modifiers

Adds the "Enhancer" component, which represents any effect which must
persist for a set period of time and provides a static change to named
attributes.  Useful for the creation of "buff," "debuff," and
"enchantment" effects.

Adds the "Modifier" component, which extends Enhancer and adds the
capacity to be "activated" a number of times per second.  Modifiers are
intended for "over time" effects or statuses, such as "poison" or
"healing."