add 'create task' button on show work item modal
display all related work items
refactor related item helper
fix last comment delete bug
Merge branch 'hotfix'

* hotfix:
  fix last comment delete bug
Merge branch 'work_item_relation'

* work_item_relation:
  refactor related item helper
  display all related work items
  add 'create task' button on show work item modal