Updated .gitignore, synced app & skel

Added some good practice rules from https://help.github.com/articles/ignoring-files to gitignore
Changed .gitignore to only ignore /app/Config/database.php instead of all files in /app/Config/ (helps to keep it in sync with its skel folder!)

Brought \app\ and \lib\Cake\Console\Templates\skel\ in sync
Fixed various @package annotations in \app\
Fixed various @package annotations in \lib\Cake\Console\Templates\skel\