Return stewardship w/ default mobile fields and search fields

Because this is adding a new type of field group that the mobile do not
have the ability to render yet, these changes are only available in v3 of
the API.

This is intended to be the final feature in v3, and all new breaking
changes should be part of v4.
If I am reading this correctly, all the collection UDFs are defined in code and bundled together in one field group. Our past customers have sometimes been picky the order in which the fields appear on the view/edit page, especially when there are a precious 320 pixels. I would like to push these out to ``mobile_api_fields`` to maintain full flexibility of inclusion/exclusion and ordering.