Allow editor to opt-in or -out of review accepted / declined / completed email notifications

[pmangahis]

Describe the problem you would like to solve
In OJS 3.3.x it looks like all the Editors assigned in the Participant list receive a notification when a reviewer declines or accepts a review request.

Describe the solution you'd like
Ability to customize (in the user profile perhaps) whether the user will receive these notifications via email. The current options in the user profile don't seem to cover this situation.

Who is asking for this feature?
Journal Editors, Journal Administrators, Technical Support

Additional information
The option to disable the template is not an ideal option as none of the users would receive the notification

[kshuttle]

+1 for this issue from a PKP PS client.

[pmangahis]

Can this be extended to include the option to opt-in or-out when a review is overdue? Or would it be better to create a new request for this?