Make it possible to configure instasearch to show all matches

[amadawn]

Currently instasearch can be configured to show at most 50 matches I believe. It'd be nice if there were more options (e.g. 100, 200...) including "all" to show all matches.

[ajermakovics]

If there are more than 50 results it will show the "More..." box at the end of results list. Clicking that gives you all results. I find that gives nice tradeoff between performance and usability so am not particularly convinced we need more options. That being said if anyone feels strongly about it and submits a pull request for this I'll happily merge it in.