Update search to use Algolia

Currently the search isn't working as it is using the old hnsearch.com API which has now been taken down. I've updated it to use the new Algolia API.

It's working however there is one potential issue that could do with looking at - I was unable to figure out what the "search type" referred to and therefore what the values of kHNSearchParamsInteresting and kHNSearchParamsRecent should be. They will need fixing - however as the search currently doesn't work at all, I hope this fix is better than nothing :-)