Update a few view changes and remove 2.x change notices.
Add TOC for cell docs.
Start expanding cell docs.
Finish first pass at cell docs.
Remove docs for deprecated features.
Fix TOC issues and add missing documents.
Update docs for shells.

* execute() -> main.
* Fix broken formatting.
* Fix broken links.
* Add missing namespace to ConsoleOptionParser.
* Correct methods moved to ConsoleIo.
Remove uncommonly used methods.

We don't need to document *every* method in the book. The API covers
these methods quite well.
Split out loading and rendering.
Reorganize.
Update docs to match what the code will be.
Merge pull request #1302 from cakephp/cell-docs

Cell docs