Allow Aha base field values to be set based on custom worksheet fields

Custom worksheets and the fields within them allow powerful formula-based derivation of values but the base Aha fields in many cases allow certain things to be driven across the application. For example, the capacity field in releases or estimate field in Story have a special meaning. But if we can capture additional information in worksheet fields and calculate estimate or capacity the way we want, it will be good to have the release capacity take that value or the story estimate pick that value than having to re-enter that.