Fixes #663 - adds phone helper for results

Fixes #663 - adds phone helper for search results so that the first
voice or hotline phone number is displayed on the search results list,
or none if either no number or only numbers of type `tty` or `fax` are
found. Also, singularizes HTML class from `phones` to `phone` for
search result entries and removes unneeded list for phones.
The HTML should be part of the Phones helper module, as a separate method. You don't need to assign the `phone` variable to the output of the method and then check for its presence. The helper method should do all this checking for you. In my suggested implementation, if there are no matches, the method will return nil, so you can just call the method directly in the view.