Update Plugins UI to reflect export plugins

[yakkomajuri]

Export plugins currently show up in order on the Plugins page, but they all use onEvent, meaning that the order they run in is actually irrelevant. This is also an important distinction.

Now that we have onEvent implemented in many plugins, and we have a way to infer plugin capabilities, we should devise a way to display plugins that only implement onEvent (i.e. not processEvent) in a better way. Having written this we probably need a way to show plugins that run jobs too.

This is a sub-point of the very general board card "Improve plugins frontend".

A few open Qs:

1. How do we want to display this?
2. What happens if a plugin implements both processEvent and onEvent - do they show up on both lists? How do we flag the distinction?

[yakkomajuri]

Done