Improve "Save" UI of Person Forms

Various person related forms follow a pattern of directly editable fields (eg: name, title, organization) and links to other views (identifiers, email), etc. This includes

/registry/org_identities/edit
/registry/co_people/edit
/registry/co_person_roles/edit

(The add versions of these pages only show the directly editable fields, so aren't really affected.)

The problem is that there is a "Save" button at the bottom of the page, but that save button only applies to the directly editable fields. This layout implies that one needs to click save when, say, adding a telephone number even though that's not the case. (Worse, it might imply one can back out of adding a telephone number when the change was already committed.)