Store listeners based on their arguments

[danpecher]

Listeners are now described using ListenerArguments which carry arguments based on data type (messages/conversations). Each ListenerArgument key has a dictionary associated with it that consists of a ListenerIdentifier as the key and the closure to be run as the value. This way individual closures can be removed independently based on the arguments and identifier.

[danpecher]

@schwarja you were right, the way I did it wouldn't really work. So I fundamentally changed how listeners are used:

• I removed ListenerIdentifier
• I used ListenerArguments to identify listeners of one set of arguments (number of items per page for example)
• I used existing IdentifiableClosure to identify closures that the user registers. Only ObjectIdentifier is returned to him so it's basically the same as before (with ListenerIdentifier - also a string)

So if someone registers 3 listeners to conversations with page size of n, they will be stored under ListenerArguments.conversations(pageSize: n) as an array of 3 IdentifiableClosures. The user will get 3 ObjectIdentifiers which he can later use to deregister given closures.

I hope it makes sense 😁