Ability to assign groups.
To assign group, user must have a right to send a message to that group.
In addition, 2 jobs were introduced, - AssignNotification and UnassignNotification to inform interested users in the background about the new assignment.
* FEATURE: Display PMs in assigned activity and differentiate them.
* FEATURE: Unassign/Re-assign tasks from the activity view
* Remove bulkAssign. Reuse assign/unassign with a service. Change PM icon position
* Reuse ListItemDefaults instead of duplicating code.
* Conditionally show/hide feature if list items defaults is present in core