Fix pagination in Haystack search

Haystack's SearchView isn't based on django CBV and uses 'page' instead of 'page_obj' in context. Simple fix was to duplicate pagination.html and use that version for the search view. This isn't DRY, but seemed a better way to me than copying the whole render_to_response function from Haystack's View (no other way without generating a new instance of the Paginator object). 

I think ditching the productlist view in the catalogue app and using/writing a searchview based on CBV would be the best choice (think there's already a fork on haystack where someone started to rewrite the searchviews). 

All necessary fields can be saved in the search_index and used in templates which will avoid hitting the database. Guess there will still be querys to determine the availability, but with a backend like elasticsearch this will probably still be faster. I'm using elasticsearch in another project and its blazing fast.