WIP: Moving AAE to riak_cire

So,
I've started moving AAE from riak_kv to riak_core. It misses documentation and is not too well tested but it seems to work in first tests.

It changes the interface to the AAE code slighty by adding two more options that get passed:

* The ring serivce (formerly riak_kv)
* The responsible vnode module

There is a riak_core_aae_vnode behavior that includes the functions the vnode needs to implement. And there still needs to move some code in there that is fairly general.

So please don't merge yet it's mostly to track progress and collect comments on the effort (and hopefully fine some people giving it a test :P)