Update authentication.rst

Removed the static reference on `user()` as it is no longer static in `alpha1`
Merge pull request #1452 from davidyell/patch-1

Update authentication.rst
Fix 're-evaluating' typo in query builder docs
Add missing _accessible property to tutorial.

Refs cakephp/cakephp#3863
Update cakephp-folder-structure.rst

Add dir `tests` to list
Merge pull request #1457 from kicaj/patch-2

Update cakephp-folder-structure.rst