Move getting help up higher.
Start moving files and content around for new intro.

The first part of the new toc will be a new intro/overview that shows
some quick code examples and overview information for CakePHP. I think
the destination TOC might not be possible, but we can get pretty close
through effective restructuring.
Merge old understanding doc into the overview.
Continue work on new intro chapter.

It is much more slim than the old one which was a bit verbose, pedantic,
and condescending in nature. I think we can add more of the explaination
into an improved tutorial, that I'll be working on soon.
Trim more fat.
Fix broken links.
Fix TOC depth.
Fix mistake.
Fix more mistakes.
Fix mistakes.
Merge pull request #1762 from cakephp/3.0-new-toc

3.0 Start new toc