This commit changes the ActionModules to allow the RestController to be
provided by an internal plugin.
It renames `RestInterceptorActionPlugin` to `RestServerActionPlugin`
and adds a new `getRestController` method to it.
There may be multiple RestServerActionPlugins installed on a node, but
only 1 may provide a Rest Wrapper (getRestHandlerInterceptor) and only 1
may provide a RestController (getRestController).