Add an "intrinsics" property

To property support game play we would need to add an "intrinsics" property as well as a "statistics" property.
The difference being that the former represents character attributes that are set, whereas the latter represents similar attributes, but dynamically calculated. This latter calculation of the "statistics" property should take into account things like buffs, spells, environment etc.

For example, the "intrinsics" property might have a "strength=10" value. But because the character is currently wielding a "Sword of Strength+1" the "statistics" property will have "strength=11".