New @RestHook annotation.

I've added a new annotation that resolves the feature request shown below.

1. JUNEAU-64 Support advanced annotated variables on methods implementing onPreCall and onPostCall

It also adds the capability for performing child resource initialization before parent resource initialization.

The change replaces the various servlet and REST call lifecycle methods with a single unifying method annotation:
http://juneau.incubator.apache.org/site/apidocs/org/apache/juneau/rest/annotation/RestHook.html

One of the nice features is that you can add as many of these annotated methods as you like to your class.  For example, instead of a single init(RestConfig) method, just add your own init methods and never have to worry about calling super.init(RestConfig).                

In order to get this to work, I did have to make the RestServlet.init(ServletConfig) final so that it can no longer be extended.  The normal HttpServlet.init() method can still be overridden, however it's probably best-practice to just use @RestHook(INIT).

I debated whether to keep these, but decided to remove them from the RestServlet class to keep things simple:

• • init(RestConfig) - Use HookEvent.INIT instead.
  • onSuccess(RestRequest, RestResponse, long) - Use HookEvent.END_CALL instead.
  • onPreCall(RestRequest) - Use HookEvent.PRE_CALL instead.
  • onPostCall(RestRequest, RestResponse) - Use HookEvent.POST_CALL instead.