Support for ransack cont_all queries

[guzart]

When using ransack's _cont_all predicate, the value expects an array of search keywords, currently only the string search value is passed to ransack.

First idea that comes to mind is to do a pre-processing of params[:q] before passing it to ransack. This way the configuration and logic can remain on the server side.

The pre-processing would check for predicates that are expecting an array of keywords and then split their corresponding value string into a keyword array