Simplify management API

[mathieucarbou]

Helping @ljacomet and @albinsuresh to introduce or modify the management integration in Ehcache made me confirm my suspicion: the management api to use client-side (to integrate into clients and server entities) is way too complicated. It requires to understand a lot of concepts and how things work in the underlying layer. It is also damn complicated to setup. It cannot be setup from scratch: it needs to be copy/pasted from an example. And that is not good.
So if we want people to be able to effectively use the management apis (with ease and without our help), things need to be simplified a lot.

I think the push api for notifications and stats is OK. But the provider system to expose management metadata that describes objects, stats and management calls is way too complicated.

FYI @anthonydahanne @lorban @GaryWKeim