Followup search updates including letting the score field have an option to set another field as the default tablesort if it is set to the default tablesort.

#375342 by dww: node_comment_statistics should be INNER joined because there is always 1:1 reference.

#375342 by dww: node_comment_statistics should be INNER joined because there is always 1:1 reference.

#353002 by neclimdul: Provide a filter for user posted or commented on to complement the argument with the same functionality.

#368234 by dww and neclimdul: Allow the "Anonymous" user to have a different (or no) name in User: name field.