Feedback Plugin Enhancement - Enable Deletion of a Feedback

[zthfmh]

What do you want to improve?

For the Feedback plugin admins should be able to delete any feedback submitted from users - this will likely need RBAC support as a prerequisite as suggested here: #1334

What is the current behavior?

The received feedback cannot be deleted

What will the new behavior be?

Admins, or generally speaking, anyone that is allowed to visit the global feedback page (with access control) is able to delete any feedback items submitted from users