Search results page

This change allows for the custom search results, as discussed in #731.

@wrightmartin Some info for styling purposes:

- The main template for the search results is `pombola/south_africa/templates/search/search.html`.
- It uses the `pombola/south_africa/templates/core/person_list_item.html` template for each person row, this is the same template used everywhere else on the site that a person row is rendered.
- Organisation rows use `pombola/south_africa/templates/core/organisation_list_item.html`, as with the person this is the site-wide template.
- Speech rows use `pombola/south_africa/templates/search/speech_item.html`, this is not a global view, it's only used in the search results.
- Each result row gets rendered into `pombola/south_africa/templates/core/generic_list_item.html`, which will automatically add the correct classes to each `<li>` element for you.