story #6933: add open/closed to milestones and submilestones

Change-Id: I6990fb9322e4ad3832f09bdaded3fd440515bbc0
Merge commit 'refs/changes/04/2504/3' of ssh://gerrit.tuleap.net:29418/tuleap into stable

* ssh://gerrit.tuleap.net:29418/tuleap:
  story #6933: add open/closed to milestones and submilestones
This is Tuleap 7.1.99.3

Change-Id: Id2787f9285e2b0fec79433af77cae28fefb133a2