PSR-2 Compliant Sniffer

This PR aims to implement PSR-2 in its entirety, as well as preserving existing CakePHP rules that do not conflict with PSR-2.

After running `php-cs-fixer` on core, and then running `phpcs` with this updated sniffer --  it's **largely** docblock indentation fails... which PHP-CS-Fixer doesn't seem to fix. :cry: 

To Do's:
- [x] Find a solution for the docblock indentations. *Taken care of by @ceeram. (https://github.com/FriendsOfPHP/PHP-CS-Fixer/pull/790) :clap:*
- [x] Update "...fail.php" test files to include correct PSR-2 standards (outside of CakePHP standards) to give a more focused/accurate test of what it's actually evaluating.

I'm opening this as a "WIP" in case I've overlooked/removed any CakePHP rules, as well for looking for any docblock indentation insight anyone may have.

This PR's eventual merge will be released as `2.0` so that continuous integration between Cake 2 and 3 can live side by side.