[FIX] web: Kanban: deal with `group_create` attribute

This attribute is used to determine one can create a new column in
the kanban view.

Before this commit, it was always true and not specified in the
controller `activeActions` (which was causing a bug where the
no content helper was displayed instead of the column quick create).

The controller was also always initiated with false so the column was
only available after an update.