Fixes some broken itemUis

After refactoring AbstractItemUi some overrides are no longer working
Adds fade out also when the user clicks on a category
Doesn't fetch subsequent pages if user is still filtering the product list
Extends getClientParams() method to enable filtering for specific prefixes
Adds methods for adding text and category conditions to an exising filter
Removes unnecessary Javascript onReady() in stock response
Adds additional class to be able to style the <nav> element
Improves speed of image loading and allows multiple search filters
Adapts tests to change in stock layout file
Adds "prefetch" to "next" link and adapts tests
Changes search filter to allow integration into the whole filter client
Merge pull request #427 from nsendetzky/2014-01-13_faceted-search

Improves speed and flexibility in catalog html clients
Merge pull request #425 from cookiekiller/master

Fixes some broken itemUis