Don't add activity and reference fields to outgoing message

[Naktibalda]

I noticed that Botkit adds some garbage fields to outgoing fields, e.g. {"type":"message","text":"Hi...","channelId":"websocket","conversation":{"id":"98f515de-b10a-4b4c-51b9-d6fa3f0e1688"},"from":{"id":"bot"},"recipient":{"id":"98f515de-b10a-4b4c-51b9-d6fa3f0e1688"}}

So I decided to remove them.

Previous activity check was incorrect and allowed falsy values to be added to channelData.
Reference fields weren't checked at all so they were sent to client.

[Naktibalda]

Actually, I don't like this patch anymore,
I think that applyConversationReference call
at https://github.com/howdyai/botkit/blob/master/packages/botkit/src/botworker.ts#L136 is completely unnecessary, because the next step strips those fields.

[Naktibalda]

I copied the good part of this change to #1708

[Naktibalda]

Another U-turn, I realized that this change was good.

[benbrown]

This fix has been indirectly incorporated into 4.5! Thanks for the contribution!

[Naktibalda]

Thanks, I upgraded to 4.5 and it is working as expected.