Centralize the plugin setup process

Many plugins have to implement a setup method which prevents them from correctly using @RequiresFacet or packaging types - because the setup method cannot be called unless the @RequiredFacets are installed, which may not be the case before setup() is executed. Plugins should be able use a @Observes or @Produces method to tie into a centralized setup system, which executes the plugin setup function sans arguments, and ignoring requirements.

$ setup myplugin

public void setup(@Observes SetupPlugin<MyPlugin> event, ...)
{
   // do setup here
}

@Produces public SetupPlugin<MyPlugin> setup(...)
{
   // do setup here
}

or perhaps something simpler, but this would need to implement some kind of parameter injection

@Setup
public void setup(...)
{
   // do setup here
}