Update auth.rst

App:uses() is needed for baking a view (for example)
Merge pull request #1603 from ptica/master

Update auth.rst: App:uses() was missing
Remove 1.3 new docs from 2.x docs.

Closes #1604
Divided the Plugin article into two sub articles
Remove leftover single doc wording
Clean up plugin doc headings
Better intro transition between plugin docs
update `Progit` website link
correct link to ProGit book
update `Progit` website link
Merge pull request #1615 from antograssiot/master

master - update `Progit` website link
Remove extra title
Merge pull request #1609 from cakephp/plugin-divide

Divided the Plugin article into two sub articles