These changes are made to milestone-related GraphQL APIs.

- Milestone type gets a new 'expired' field indicating
whether milestone's due date is past the current date.

- When listing milstones, these arguments can be specified:

  - 'expiredLast' sorts milestones in layers:
  Current miletones are placed first, followed by
  milestones without due dates and expired milestones.
  Within layers, milestones are sorted by due date
  (asc by default) with ties being broken by id (desc).
  When 'expiredLast' is set, 'sort' argument other than
  due_date_desc or due_date_asc is ignored.

  - 'sort'

Changelog: added