Add Transforms to Properties

**Is your feature request related to a problem? Please describe.**
It would be nice to not have to be picky about capitalization. If a value must be 'FOO' or 'BAR', couldn't there be a post-parse step that would accept a transform to convert the value to UCase?

Similar things could happen for other types of values: Round to the nearest X, absolute value, etc.

**Describe the solution you'd like**
A transform step, that happens after parse but before validation.

**Describe alternatives you've considered**
Types can be used to do this during parse, but its more involved and easy to break contracts. Easier to have a simple transformer that anyone could plug into with a lambda.