fix: Improve transport-commons types

[vonagam]

Normalise types of PublishMixin, ServiceAddons and Application for publish/registerPublish:

• an event is string or ALL_EVENTS symbol.
• callback is now publisher in argument and variable naming.
• a publisher returns a channel, an array of channels, void or a promise* for those.
• return value is this.

* - before a promise was not present in types and not mentioned in documentation, but based on this line it is possible currently to return a promise. We can remove this feature from types and remove Promise.resolve from that line if this should not be supported.

Plus small performance improving in publishing: no point in creating array, using _.get and then .find with typeof when simple or condition will do (ideally publisher should be cached).

[daffl]

Nice, thank you! Will go out with the next pre-release.