Pass functions to register method from inputs instead of methods

[hlxid]

Finishes fix of #89.

The problem was that we passed methods to the register/unregister methods, which take functions. In these cases scala will convert the methods to anonymous functions e.g. in the TwitchChatInput start part onMessage will get changed to x => onMessage(x). Because of this the function passed in the start method is not the exact same object as the one in the stop method, the handler of the input wasn't removed in the connector.

Note that I only have tested this with the twitch chat input, but the handler logic similar in all other connectors it should work there too.

In the future we probably want to generalize connectors that have event handlers with some trait. Then we could place a implicit identifier in the inputs and have the connector unregister all handlers that were registered with a identifier when the plugin stops. Thats a way cleaner solution, but will require more time, so this is just for the 2.1 hotfix.

[J0B10]

Wow, that was quick, thank you 👍