`registry:list` to list entities, and events

[mattbishop]

This may take a little thinking, but we want to show all the events registered for an entity, and another command to list the entities themselves. For larger systems with hundreds of events, a full list gets to be difficult to use.

[evert]

Some ideas for the interface, let me now what you think:

# Show all entities
evently registry:list-entities

# Show all entities for an event
evently registry:list-events --entity foo
evently registry:list-events -e foo

Perhaps all these commands can have a -v for verbose flag that shows the name + the URI ?

[evert]

@mattbishop Does the above syntax work for you?

[mattbishop]

LGTM