Paginator can now use string or simple arrays for "order

"order" => "Posts.id" wasn't use by the paginator
It was expecting [key => order, key => order]
Removed unused test and simplified validateSort
Fixed code formating
Fixed some typos
Merge pull request #2736 from Grafikart/3.0-fix-paginator-order

Paginator can now use string or simple arrays for "order