Add current_user_id to gon vars

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Add only open/reopen scopes to issues

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Add js milestone class. Activate drag-drop for issues on milestone page

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Add reopened tab to milestone issues. Add ids and data to milestone issues to enable dragging

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Fix tests

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Milestone drag-n-drop with 3 columns

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Merge branch 'milestone-issues-dragging' into 'master'

Milestone issues dragging

This is part of #1207.
I will submit this feature with small but finished merge requests.