Remove ApiShell

I propose to remove the ApiShell class from the core - in favor of a plugin solution.
Maybe we can put it in Utils or another plugin of some sort.

Working with Cake like forever I have never even knew that one existed, nor did I ever need it.
Especially with having the source code, complete doc blocks and context included. But there is also a good online documentation and API available.
I see no real use for that class - as a part of the core. What do you think?