Add flush button to clear all redirects

[Sebobo]

Sometimes it's helpful to clear all redirect after exporting and working on the list of all redirects. Especially if the intent of the new list is to also clear out old redirects.

A new button would be added at the footer of the list or in a separate view to delete all or a subgroup of redirects.

A prompt should verify if the redirects should be deleted.

An additional privilege should limit the possibility to delete all redirects for user groups.