Pluggable rendering system

[bernhardttom]

(this feature request added on behalf of a user)

Quote: Esper's JSON and XML render features are quite good. The features are useful and the internals are optimized. We'd like to render events to different formats of our choosing. Support for something like a EventRenderer<T> would help, especially if an abstract superclass exposes functionality similar to RendererMeta, which is currently an internal class but would make it much easier to write concise and performant custom renderers.