Feature: on UI optionally removing delete link only on running process

[alessandrofuda]

Since I'm working with longtime processes using the integrated UI, I think might be useful to give users the ability to disable (removing) the delete button only for running processes.

Why? Because during a longtime process, if user click on delete link, the job item is removed from UI, but the process behind it is Not killed. This might generate confusion and ambiguity, especially if there are more chained jobs. So, imho, It's better don't give user this availability while job is running.

So I propose to add in config/queue-monitor.php something like this:

ui.allow_deletion_on_running_jobs => true/false

If you agree, I can PR it.