Simplify user cache management of data forms
Summary: Ref T4103. Ref T10078. We currently have separate "usable" and "raw" values, but can simplify this by making newValueForUsers() return the raw value.
Test Plan: Ran unit tests; browsed around; dropped caches and browsed around.
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T4103, T10078
Differential Revision: https://secure.phabricator.com/D16043