Make the $results array that comes back from a search more useful.

In particular I used modify_query to add a field to the $params['fl'] and was disappointed that the field wasn't automatically available to me in the search results. It was, in fact, available, but only through the badly named 'node' element of the array which contained the Apache_Solr_Document. I could have used the $result['node']->getField('blah'); method but imo this assumes too much knowledge of the phpclient library.

To make it easier to deal with this patch does two things.

1. renames 'node' to 'document'. Note that this creates some mismatch between the array and the theme layer. If it causes problems we have to address the theme layer.

2. iterates over the Apache_Solr_Document and makes an array of its fields called $result['fields'] for easy access.