JShell API review 2: onSnippetStatusChange/SnippetStatusEvent -> onStatusChange/SnippetEvent

[Robert Field]

> 
> onSnippetStatusChange -> onStatusChange or onSnippetEvent
> 
> SnippetStatusEvent -> SnippetEvent

Thinking about this more: SnippetEvent can be triggered without a status change.  That would argue for changing the names to: onSnippetChange/SnippetEvent

However, that could occur before with a source change.  With source Snippets replacing keys, a source change will trigger an overwrite.  So, now, this can only occur with an update that while it does not change status, it could change semantics.  I can’t really think of anything useful that would be done with a: this Snippet could possibly have changed semantics event.  

If the status non-charging events are filtered out, the existing name is more descriptive — and answers the question asked in previous reviews: status of what?

-Robert