Fix images on home, search & cateogry pages: 27444

@prabinv @texasag @kevinsproles & @tsanko for completeness

I added a filter to parse images form the product.imageCollections object.
By default it returns the image for 'default' & 'medium' but that can be overridden with arguments to the filter fn. 
What does the value `'http://test.c'`signify?