Added responsible to bulk update
Added responsible to context menu
Fixed non-functional delete via context menu
Added responsible to work_package notification mails
Removed old timelines helper for getting available responsibles
to unify ordering for possible assignees and responsibles on work_package
edit
Fixed nasty bug
Merge remote-tracking branch 'origin/dev' into feature/responsible_on_bulk_edit_and_context_menu
Adds changelog entries
Merge pull request #860 from opf/feature/responsible_on_bulk_edit_and_context_menu