Design and Implement Component Events about vugu

[bradleypeabody]

One idea on this was to use simple struct fields of type func to wire up events. However, it is very possible that we will need a way for these events to cascade up to parents. If this is the case, then we probably have to model something after DOM events (not sure if the capture phase is needed). But this does add a lot of complexity.

Probably we need a more exact list of cases, off the top of my head:

• Nested components a -> b -> c; c broadcasts an event that b doesn't listen to but a wants to.
• Root component gets a lifecycle event or some sort of event and a nested component wants to know when this overall global thing happened (such as the styles (or JS) now being loaded).

[bradleypeabody]

This is implemented now: https://www.vugu.org/doc/components#component-events

Broadcasting did not get implemented because we don't have a use case. This was much simpler to do without having to build some sort of listener system with propagation etc. Component events are just method invocations, and until/unless we find a very strong case for making them otherwise it'll stay that way.