[FrameworkBundle][Command] print registered event-listeners + event-subscribers

|Q|A|
|--:|:--:|
|Bug fix?|no|
|New feature?|yes|
|BC breaks?	|no|
|Deprecations?|	no|
|Tests pass?|	yes|
|Fixedtickets|	|
|License|	MIT|

New console-command for the event-dispatcher. The command prints a table like the `container:debug` command with all registered events and their event-listeners. 
The list is sorted by events.
There is an additional argument `event`. If this parameter is set, the command prints the listener for the event.