Provide structure in the registry for distinguishing types of options

[macchiati]

I think in the registry we need to be very clear about the following classes of effects that an option can have. (Of course, an option may do more than one of these)

• an option effectively supplies input in addition to the operand (eg, timezone, currency, ...)
• an option that modifies the formatting of the operand (eg, mix/max fractional digits)
• an option that modifies the selection of an operand (eg, also mix/max fractional digits)

We'll also have functions that transform the underlying value of an operand (we don't have any right now, but we will absolutely need that for offsets in order to support a core MF1.0 feature).