Support designating a contact number as "primary"
Since this interacts in weird ways with "disable", just do a "when any number is touched, put all of the user's rows into the right state" sort of thing.
- Added numbers, made numbers primary, disabled a primary number, un-disabled a number with no primaries. Got sensible behavior in all cases.
Reviewed By: amckinley
Maniphest Tasks: T920
Differential Revision: https://secure.phabricator.com/D20011